EP0177885A2

EP0177885A2 - Method and device for registering printing press

Info

Publication number: EP0177885A2
Application number: EP85112433A
Authority: EP
Inventors: Daiji Suzuki; Kenji Yamada; Michiaki Kobayashi
Original assignee: Dai Nippon Printing Co Ltd
Current assignee: Dai Nippon Printing Co Ltd
Priority date: 1984-10-03
Filing date: 1985-10-01
Publication date: 1986-04-16
Also published as: EP0177885A3

Abstract

57 Disclosed in this specification are (1) a registering method for a printing press comprising the steps for magnifying a pattern of a printed medium and displaying it on a display device; inputting the coordinates of a position of each color pattern for a predetermined element of the magnified and displayed image by coordinate input means; determining a registration error between respective colors based on the coordinates of each color position and the magnification of the image; calculating a quantity required for adjustment of the position of a plate cylinder based on said registration error; and effecting the registering of the printing press depending upon the results of this calculation: (2) a device for inputting a pattern of a printed medium on a printing press, displaying the pattern on enlarged scale on the screen of a display device, inputting the coordinates of the position of each color pattern for a predetermined element within the magnified and displayed image by coordinate input means, determining a registration error between respective colors from the coordinates of the position of each color and the magnification of the image, calculating a quantity required for the adjustment of the position of a plate cylinder based on said registration error and effecting the registering of the printing press in response to the results of this calculation: and (3) a device for displaying a pattern of a printed medium on enlarged scale on the screen of a display device, inputting the coordinates of the position of each color pattern by a friction input means by utilizing a predetermined element within the magnified and displayed image and determining a registration error between respective colors from the coordinates of the position of each color and the magnification of the image.

Description

The present invention relates to a method and device for registering a multicolor printing press and a device for determining registration errors.
For instance, in the case of an offset press, a plate with a pattern is wrapped around a plate cylinder and an ink which is stored in an ink fountain is applied to the plate through a group of inking rollers. The ink applied to the plate is pressed against the plate cylinder and transferred to a blanket (rubber) cylinder which is rotating. A web or sheet of paper is made to pass between the blanket cylinder and an impression cylinder, whereby a pattern is printed on the web or sheet of paper. In the case of the multicolor printing, a unit comprising a plate cylinder, a blanket cylinder and an impression cylinder is provided for each color. The web or sheet of paper printed with a first color is made to pass the printing unit of a second color and then the printing unit for a third color, whereby multicolor printing is accomplished.
Meanwhile in the multicolor offset printing process, when a plate wrapped around a plate cylinder is deviated from a predetermined position, a printed medium has registration errors in the circumferential direction (in the direction in which the web or sheet of paper is transported), the lateral direction and/or in the twisted direction.
Therefore after a trial printing, an operator visually observes the print by means of a magnifier or the like to determine a registration error and in response to the registration error thus found, the operator adjusts the positions of the plates. These steps are repeated until the registration errors are completely eliminated.
However, in order to visually measure registration errors and adjust the positions of plate cylinders in response to the registration error thus found, an operator must have great skill and long experience. Furthermore, the above-described steps must be repeated many times in a trial-and-error manner until all registration errors are eliminated so that much time is required and much printing paper is wasted.

SUMMARY OF THE INVENTION

In view of the above, a first object of the present invention is to provide a simple method for correctly measuring registration errors of a printed medium and effecting the registering in response to the results of this measurement.
A second object of the present invention is to provide a device for measuring correctly registration errors of a printed medium by a simple operation and automatically effecting the registering of a printing press in response to the results of this measurement.
A third object of the present invention is to provide a device capable of measuring a registration error of a printed medium in terms of a numerical value by a simple operation whereby the amount for adjusting the plate is determined in response to the measurement.
To the above and other ends, firstly the present invention provides a registering method for a printing press comprising the steps of magnifying patterns of a printed medium and displaying it on the screen of a display device; inputting the coordinates of positions of each color pattern for a predetermined element of the magnified and displayed image by coordinate input means; determining registration errors between respective colors based on the coordinates of each color position and the magnification of the image; calculating quantities required for the adjustment of the positions of plate cylinders based on said registration errors; and effecting the registering of the printing press depending upon the results of this calculation.
Secondly, the present invention provides a device for inputting a pattern of a printed medium on printing press, displaying the pattern on enlarged scale on the screen of a display device, inputting the coordinates of the positions of each color pattern for a predetermined element within the magnified and displayed image by a coordinate input means, determining registration errors between respective colors from the coordinates of the positions of each color and the magnification of the image, calculating a quantity required for the adjustment of the position of plate cylinders based on said registration errors and automatically effecting the registering of the printing press in response to the results of this calculation.
Thirdly, the present invention provides a device for displaying a pattern of a printed medium on an enlarged scale on the screen of a display device, inputting the coordinates of the positions of each color pattern by a friction input means by utilizing a predetermined element within the magnified and displayed image, determining registration errors between respective colors from the coordinates of the positions of each color and the magnification of the image and outputting to display and/or print out the amount for adjusting the plate in response to the registration error.
Therefore, according to the present invention, the registration can be achieved only by one trial printing so that the operation time and paper can be considerably reduced.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a perspective view used to explain a first embodiment of the present invention;
FIG. 2 is a view used to explain the relationships between the printing unit motors and plate cylinders of the first embodiment when the adjustments are made;
FIGS. 3(a) - (f) show images displayed on a color cathode-ray tube shown in FIG. 1;
FIG. 4 is a flowchart showing the steps of arithmetic operation carried out by a computer shown in FIG. 1;
FIGS. 5(a) - (f) are views used to explain the contents of arithmetic operations corresponding to the steps shown in FIG. 4;
FIG. 6 is a view to explain another embodiment of the present invention;
FIG. 7 is a view used to explain a printout obtained from the embodiment as shown in FIG. 6;
FIG. 8 is a view used to explain the present invention applied to a sheet-fed printing press;
FIG. 9 is a view used to explain a pure optical system for displaying on enlarged scale a pattern on a display screen;
FIG. 10 is a view used to explain a registering device in accordance with the present invention;
FIG. 11 is a block diagram thereof;
FIGS. 12a and 12b show a flowchart used to explain the mode of operation of the device shown in FIGS. 10 and 11; and
FIG. 13 shows a registration mark having a special configuration which may be used in the present invention.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

The preferred embodiments of the present invention will be described with reference to the accompanying drawings.
FIG. 1 shows a first embodiment of the present invention which is applied to an offset press. A printed medium to be measured X is placed on a table 1 and a suitable portion of the printed medium X is magnified and focused through a magnifying lens 2 with an extension tube. The magnified light image thus formed is converted by a color video camera 3 into electrical signals which in turn are applied through a superimposer 5 to a color cathode-ray tube 4 which displays an image magnified by tens of times. It is preferable that a pattern of the printed medium X to be displayed on the color cathode-ray tube 4 include a pattern which can distinctly indicate the misregistration. For example, it includes registration marks or patterns whose misregistration can be easily recognized. An image such as a cross-shaped cursor which is generated by a personal computer 6 is superimposed through the superimposer 5 on the image displayed on the color cathode-ray tube 4. This cross-shaped cursor can be displaced in response to the operation of a joy stick 8 connected through an interface 7 to the personal computer. After the cursor is displaced in response to the operation of the joy stick 8, an input instruction is applied by means of an operation panel 9 whose input instruction buttons include "circum", "lateral", "upper surface", "lower surface", "operation", "man side", "gear side", "BL", "C", "M", "Y" and "needle".
The coordinate inputs obtained by the operation of the operation panel 9 in response to the shift of the cursor by the joy stick 8 to the pattern picked up by the camera 3 and displayed on the color cathode-ray tube 4 is calculated by the personal computer 6 and the calculation results; that is, the registration errors are converted into data for correcting the positions of a plate cylinder. The data is then applied through an interface 10 to motor drive circuits 11 so that the motors M are energized, thereby adjusting the positions of the plate cylinders.
In addition to the camera 3, as input means, a flat scanner may be used. Alternatively, the register mark on a printed medium may be directly made into contact with an image pickup tube or an image pickup element. Furthermore, the register mark is photographed by use of a Polaroid camera and a hard copy thus obtained is placed upon a digitizer to enter the position of the register mark. Instead of the color cathode-ray tube 4, a display device such as a liquid crystal display device or a plasma display device may be used.
FIG. 2 shows the couplings between motors M and plate cylinders.
Each printing unit comprises an upper blanket cylinder 20, a lower blanket cylinder 21, which are pressed against each other, an upper plate cylinder 22 pressed against the upper blanket cylinder 20 and a lower plate cylinder 23 pressed against the lower blanket cylinder 21. The helical gear 20a carried by the shaft of the upper blanket cylinder 20, the helical gear 21a carried by the shaft of the lower blanket cylinder 21 and the helical gears carried by the shafts, respectively, of the upper and lower plate cylinders 22 and 23 are in mesh with each other so that the above-described blanket and plate cylinders 20 - 23 are rotated in synchronism with each other. The shaft 24 of the lower blanket cylinder 21 is drivingly coupled to a drive shaft 30 driven by a motor 29 through a pair of bevel gears 25 and 26 and a pair of helical gears 27 and 28.
The shaft 31 of the upper print cylinder 22 is connected to a circumferential error conrrection motor 32, a lateral error correction motor 33 and a twisted error correction motor 34. In like manner the shaft 25 of the lower plate cylinder 23 is connected to a circumferential error correction motor 36, a lateral error correction motor 37 and a twisted error correction motor 38.
The outputs from the motor drive circuit 11 (see FIG. 1) are applied to the respective motors incorporated in this device so that the positions of the plate cylinders are automatically corrected.
FIGS. 3(a) - (e) show the images displayed on the screen of the color cathode-ray tube 4 (see FIG. 1). FIG. 3(a) shows misregistration display marks called register marks and cyane, magenta, yellow and black marks are marked on the gear side and on the operating side of the plate cylinder. FIG. 3(b) shows suitable portions of patterns instead of the register marks. It is preferable that these portions of respective color patterns can be readily found to be misaligned from each other as shown.
FIG. 3(c) shows a cross-shaped cursor 111 which is superimposed on the patterns or marks shown in FIG. 3(a) or (b). This cursor can be shifted to any position on the screen of the color cathode-ray tube 4 in response to the operation of the joy stick 8. FIG. 3(d) shows the points of the patterns upon which the cursor must be registered and there are two kinds of inputs.
A first kind of input is used to correct in the vertical and horizontal directions of the screen of the color cathode-ray tube 4. When patterns on a printed medium are inputted by means of a camera, an operator sets the printed medium on the table 1 so that the circumferential and lateral directions of the printed medium will not coincide with the coordinates on the screen of the color cathode-ray tube 4. When a reference line representative of the vertical direction and a reference line representative of the horizontal or lateral direction are marked on the color cathode-ray tube 4 and if the operator sets the printed medium in such a way that one of the color register marks coincides with these reference lines, then the circumferential and lateral directions of the printed medium coincide with the coordinates on the screen of the color cathode-ray tube 4. However, this step is cumbersome in practice. Therefore, according to the present invention, even when the printed medium is arbitrarily set on the table, the coordinates are corrected by means of the personal computer. For instance, two points 113 and 114 on the vertical or horizontal line of one of the color register marks displayed on the screen of the color cathode-ray tube are entered. If the two points are vertically spaced apart from each other, the "circum" button is depressed. On the other hand, when the two points are spaced apart from each other in the horizontal direction, the "lateral" button is depressed. Then, the vertical and horizontal directions can be automatically corrected. A second kind of input is used to designate the coordinates of each of the color register marks. In general, the register mark is in the form of a cross so that when the point of intersection between the vertical and horizontal lines is entered as an input, both the vertical and horizontal coordinates are also entered simultaneously.
In addition to the cross-shaped register mark, there are register marks with only a vertical or horizontal line. In the latter case, the coordinates representative of the direction of a vertical or horizontal line are entered as an input. In order to input, it suffices to input only one arbitrary point on the horizontal or vertical line. The coordinates of a position are determined in a coordinate system which in turn is determined in response to the corrections in the circumferential and lateral directions. However, in this case, only the circumferential or lateral operation is carried out so that the operation panel is provided with a button for operation only in the circumferential direction and a button for operation only in the lateral direction.
FIG. 3(e) shows another example of inputting the circumferential or lateral direction. According to this method, the vertically upward direction of a register mark is always displayed in the vertically upward direction on the screen of the color cathode-ray tube. When an angle between the vertical of the screen of the color display cathode-ray tube and a line interconnecting between two points selected on the screen of the color cathode-ray tube is less than 45° as indicated by 8, it is recognized that the vertical or circumferential input is made and on the other hand, when the angle is greater than 45° as indicated by 0, it is recognized that the horizontal or lateral input is made. Therefore one button on the operation panel 9 can have a dual function of the "circum" and "lateral" buttons.
FIG. 3(f) is used to explain how to make an input of coordinates which are in common in upper surface and lower surface. In the case of the offset press, the register marks are placed substantially at the same position on the upper and lower surfaces of the printing press and must be aligned with each other. Therefore a needle hole 115 is formed adjacent to the register marks and is used to make the inputs of the misregistrations on the upper and lower surface. This can be done by manipulating the operation panel 9 as in the case of inputting the register mark position coordinate system. The upper and lower surfaces can be registered with each other based on the position of the needle hole as a reference.
The above-described input operations may be summarized as follows:

i) Input for correction in the circumferential or lateral direction:
- The joy stick 8 is operated in such a way that the cursor on the screen of the color cathode-ray tube 4 is sequentially registered with two points on the horizontal or vertical'line of a register mark. Thereafter the "circum." or "lateral" button on the operation panel 9 is depressed
ii) Input of coordinates of positions of each color pattern:
- The joy stick 8 is so operated that the cursor is registered with each of the color registration patterns and then the "man side" or "gear side" button, the "upper surface" or "lower surface" button and the "BL", "C", "M" or "Y" are depressed.
iii) Input of coordinates which are in common in both upper surface and lower surface:
- The joy stick 8 is so operated that the cursor on the display screen of the color cathode-ray tube 4 is aligned with the needle hole formed adjacent to the register marks and then the "needle" button on the operation panel 9 is depressed.
iv) The "operation" button is depressed:
- The operation is started according to the contents of the computation to be described below. FIGS. 4 and 5 show the arithmetic operations carried by the personal computer .6 as shown in FIG. 1. FIG. 4 shows the steps and FIGS. 5(a) - (f) show the contents of the arithmetic operations. According to the first embodiment, the registration error is not computed, but the plate cylinder corrections are directly computed. The arithmetic operation steps comprise the depression of the operation button (S-1), the circumferential (lateral) direction correction (S-2), the coincidence of the coordinates on the upper and lower surfaces (S-3), the arithmetic operation for obtaining the corrections of the twisted plate cylinder '(S-4), the arithmetic operation for obtaining the correction of the plate cylinder in the circumferential and lateral directions (S-5) and the application of signals to the motor drive circuit in the registration device of the printing press (S-6). The arithmetic operations are carried out by the four steps S-2 -- S-5 so that these steps.will be described in detail hereinafter.

1) Circumferential (Lateral) direction correction (FIG. 4, S-2):
- First the coordinates of the position of the register marks which are based on the X- and Y-axes (FIG. 5(a)) are converted into the coordinates based upon the circumferential and lateral direction in response to the circumferential and lateral direction information previously entered (FIG. 5(b)). In FIG. 5(a), (a,b) and (c,d) are coordinates of the position of the register mark based on the X- and Y-axes on the screen of the color cathode-ray tube and the coordinates (a',b') and (c',d') shown in FIG. 5(b) are those based on the X'- and Y'-axes with reference to the circumferential direction entered as an input. This operation is repeated four times for the gear side, the operation side and their upper and lower surfaces of one printed medium.
2) Coincidence of the upper and lower surface coordinate systems (FIG.4, S-3):
- In order to register all the register marks on the upper and lower surfaces, the coordinate transformation is carried out so that the upper surface and lower surface coordinate systems coincide with each other. For instance, FIGS. 5(e) and (f) show the conditions of the upper and lower surfaces when the circumferential directions are transformed so as to coincide with the Y'-axis. In these figures, (o,p) and (q,r) are coordinates and ^* represents a needle hole.
- In the case of the coincidence operation, the origin O is shifted to the pin hole (u,v) as shown in FIG. 5(e) and then shifted to the pin hole (s,t) as shown in FIG. 5(f) so that only the X'-axis sign of the register mark is changed.
  
  Then, the register marks on the upper and lower surfaces can be placed on the same coordinates.
3) Arithmetic operation for obtaining the correction of the twisted plate cylinder (FIG. 4, S-4):
- A twist is calculated by using the coordinates in which the circumferential direction (lateral direction) is corrected and which is converted into the coordinates in common both on the upper and lower surfaces by the above-described steps 1) and 2). FIGS. 5(c) and (d) show examples of the registration marks on the man and gear sides. In this case, BL (black) is twisted relative to C (blue) by
  (to circumferential direction)[(j-1) -(f-h)] x m where m is a constant inherent to a printing press.
- As described above, a twist for each color is obtained based on the reference C (blue) and a twisted shift is defined by a value obtained when an average twist is subtracted from the twist of each color. The corrections of the plate cylinders in the twisted direction can be obtained from the twisted shift and the magnification.
- The twist varies depending upon the width of a web of paper. Therefore, when the above-stated calculations are made on a web of paper having a standard width in order to obtain a correct twist, an error occurs when the width of a web of paper varies. Therefore, the width can be entered by using ten keys or one of the paper width selection keys is depressed depending on the width of a web of paper used so that the constant.m may be varied. A plurality of paper width selection keys are previously provided depending upon the widths of webs of paper to be used.
4) Arithmetic operation for obtaining the corrections of the positions of the plate cylinders in the circumferential and the lateral directions (FIG. 4, S-5):
- As the results of the above-described operations 1) and 2), the positions of the register marks are represented in the same coordinate system on the upper and lower surfaces of the gear and man sides so that the shifts in the circumferential and lateral directions of the register marks so that they coincide with each other can be obtained by a simple arithmetic operation.
- For instance, the shifts are obtained by coinciding all the register marks with an average position in the circumferential, lateral and twist directions, but except the register marks which are extremely deviated, it suffices to obtain an average position. From these shifts and the magnifying power, the corrections of the positions of the plate cylinders in the circumferential and lateral directions can be obtained.

The embodiment shown in FIG. 6 is provided with the printer 12 instead of the interface 10, the motor drive circuit 11 and motor M of FIG. 1 so that the amounts for adjusting the positions of the plate cylinders thus determined are printed out by the printer 12 without automatic adjustment of the position thereof.
FIG. 7 shows one output example derived from the printer 12; that is, the results of the arithmetic operations carried out by the personal computer 6.
After the input operations i) - iv) described above, upon depression of the "operation button" on the operation panel 9, the personal computer 6 (See FIG.6) calculates based upon the magnification of the color pattern, information concerning the positions of the color patterns on the screen of the display device 4 and the information concerning the circumferential (lateral) direction on the screen of the display device 4 so that the registration errors between the respective color patterns can be obtained. It is more preferable that the personal computer is so designed and constructed that it can calculate optimum corrections of the positions of a plate cylinders.
The printout example as shown in FIG. 7 will be described. This is an example of a printout of an optimum correction of the positions of plate cylinders. + represents the operation side in the lateral direction, the forward direction when twisted and the operation side in the circumferential direction while - represents the rearward direction in the circumferential direction and when twisted and the man side in the lateral direction. The unit of the numerical values shown is 1/100 mm. Therefore, for instance, BL (black) on the upper surface should be displaced by 5/100 mm in the forward direction in the circumferential direction, should be displaced by 1/100 mm toward the gear side in the lateral direction and should be twisted by 2/100 mm in the forward direction. References are upper side M (magenta) in the circumferential direction, lower side M (magenta) in the lateral direction and lower side C (cyan) in the twisted direction, which are all determined by the calculations.
Therefore when the position adjusting device of the printing press is activated in response to the printed out numerical values, the registration can be achieved for one time.
FIG. 8 shows a sheet-fed press to which is applied the present invention. The sheet-fed press prints the upper and lower surfaces of a sheet of paper separately so that when the lower surface is to be printed after the upper surface has been printed, it is preferable to utilize the patterns on the upper surface which have been already registered with each other.
In view of the above, as shown in FIG. 8, a glass plate 41 is embedded into the table 1 and a lamp 42 is disposed below the glass plate 41. The light emitted from the lamp 42 is.trnasmitted through a printed medium X and is focused by a lens system 2. Therefore, it becomes possible to observe from the lower surface side the register marks which are registered with each other on the upper surface. As a result, when viewed from the lower surface side, not only the register marks marked on the lower surface but also the register marks marked on the upper surface can be observed. Then it becomes possible to observe how much the deviation of the register marks printed on the lower surface from the register marks on the upper surface is.
In this case, instead of the "needle" button, the operation panel 11 is provided with an input button for entering the position of the register mark printed on the upper surface of the sheet so that the position of the register mark printed on the upper surface when viewed through the printed medium X is entered and the register mark on the lower surface is aligned with the register mark on the upper surface. The input of the coordinate positions of the register marks on the lower surface as well as the input of the circumferential (lateral) direction are substantially similar to that described above with reference to the rotary press. Otherwise a pinhole is provided at the centers of register marks so that the registration is rendered depending upon this pinhole. In this case the optical system shown in FIG. 8 is not needed.
In the embodiment shown in FIG. 6, the camera is used, but in an embodiment shown in FIG. 9, a combination of a focusing glass and a lens system is used. A printed medium X placed on the table 1 is magnified by an objective lens 53 and a magnifying lens 54, redirected by a mirror 55 and focused on the focusing glass 56. The printed medium X is sufficiently illuminated by the light emitted from a lamp 51 and redirected by a half mirror 55.
In this embodiment, the coordinates of the position of each color register mark is entered as an input through a transparent digitizer 57 bonded over the focusing glass 56 and is processed by a special microcomputer (not shown). Instead of the transparent digitizer, a conventional digitizer may be used and the digitizer used may be of an optical type, an ultrasonic type or a transparent electrode type.
FIGS. 10 and 11 show a further embodiment of the present invention. FIG. 10 is a schematic view thereof and FIG. 11 is a block diagram thereof. Two high-speed color video cameras 101 are disposed in such a way that they can pick up the images of the upper and lower surfaces, respectively, of a printed medium upon which are printed all color images. Each camera 101 is provided with a stroboscope 106 so that the pattern on the printed medium which is transported at a very high speed can be inputted as a still image. The inputted image is magnified by a magnifying lens 105 with an intermediate ring and is displayed on the screen of a display device 204 at the magnification ratio of tens times. In response to a control signal from a central processing unit 206 within a main body 150, the inputted image is recorded by a video tape recorder (VTR) 104 and upon depression of the "upper surface display" or "lower surface display" button on a keyboard 203, one of the images is displayed as a still image on the screen of the color cathode-ray tube 204 through a superimposer 205. Upon depression of the "input" button on the panel 203, one frame is inputted. The camera is carried by a rail 102 which in turn is disposed transversely of the passage of a web of paper so that the camera can be moved transversely of the web of paper and can input at any position transversely of the web of paper as will be described in detail hereinafter. A rotary encoder 107 is carried by the shaft of a plate cylinder and the angle of rotation of the plate can be detected in response to the signal from the rotary encoder 107. For instance, in the case of an offset rotary press, if the paper path from the plate to a point immediately below the camera is known, the position of the pattern in the flowing direction which is within the view of the camera can be calculated from the angle of rotation of the plate. In this embodiment, first the position and coordinates of the printed pattern on the upper surface which is to be inputted are entered by using ten keys on the operation board 203 and then the "input" button on the keyboard 3 is depressed. Then the position of the printed image within the field of view of the camera is calculated in response to the signal from the rotary encoder 107 and when the position of the printed pattern coincides with the coordinates of a printed pattern to be inputted, a control signal is applied to a flash circuit 109, thereby flashing the stroboscope 106. Furthermore, in response to the position coordinates of a printed pattern to be inputted which are entered by the depression of the ten keys on the operation board, a control signal is derived from CPU 206 and is applied to a motor drive circuit 108 so that a motor 103 for shifting the camera is energized and consequently the camera can be automatically moved transversely. Instead of the stroboscopes 106, a mechanical or electrical shutter can be used so that the printed pattern can be exposed for a predetermined short period of time. In addition, when the speed of the web of paper is sufficiently slow, a conventional video camera may be used instead of the high-speed video camera. Moreover, instead of the VTR 104, a frame memory may be used. Furthermore, when the printing press is stopped when a printed pattern to be inputted reaches a predetermined position, the video tape recorder 104 and the stroboscope 106 which are used to obtain a still image can be eliminated.
In one modification, the image recording devices such as VTR 104 are not used. Instead, a camera continuously inputs and in synchronism with the rotation of the plate cylinder, a stroboscxpic flash lamp is flashed or a shutter is opened and closed so that the still images are intermittently displayed on the screen of CRT 204. In this case, one may view a continuous still image.
In the case of the rotary offset press, the register marks on the upper and lower surfaces of the web of paper must be aligned with each other. Therefore according to this embodiment, a camera is disposed on the lower surface side of the web of paper and is moved to a position where the camera is in opposed relationship with the camera on the upper surface side with the web of paper being sandwiched therebetween so that both the upper and lower surfaces of the web of paper can be simultaneously inputted and any given point on the printed medium can be inputted both from the upper and lower surfaces. When the "upper surface display" or "lower surface display" button on the keyboard 203 is selected, the image picked up by the upper or lower camera can be displayed on the screen of the display device,CRT (204).
It is preferable that a portion of the printed medium whose misregistration can be distinctly observed; that is, the register marks or printed patterns from which the misregistration can be indicated be inputted. An image such as a cross-shaped cursor which is derived from CPU 206 is superimposed through a superimposer 205 on the image displayed on the screen of the display device 204. The cross-shaped cursor can be displaced by means of a joy stick 201 connected through an interface 202 to CPU 206. After the cursor has been displaced by the joy stick 201, the input instruction is entered by means of the keyboard. The color position coordinate input instruction buttons on the keyboard 203 are "operation", "BL", "C", "M" and "Y". The cursor is displaced by operating the joy stick 201 to the position of the image picked up by the camera and displayed on the screen of the display device 204 and the coordinate input obtained by operating the operation key board 203 is calculated by CPU 206. The result of the calculation which represents registration errors are converted further into corrections of the positions of the plates cylinder and are applied through an interface to a motor drive circuit 212. As a result, the motors M are energized so that the positions of the plate cylinders are adjusted.
Referring next to FIGS. 11 and 12(a) and (b), the flows of the signals and the mode of operation of the device will be described. In the first step S21, the keyboard 203 is operated so that the position on the plate cylinder of a pattern to be inputted (photographed) is entered. In this embodiment, the upper and lower surfaces of the man and gear sides are inputted at two positions so that first the position of the register marks on the gear side is entered. The keyboard 203 is connected through an interface 120 to a data bus 130. In the step S22, in response to the signal from the keyboard, CPU 206 transmits a signal to a motor drive circuit 108 so that the motor 103 is energized to shift the cameras. In the steps S23 and S24, the position of the cameras is converted into a signal by means of a position sensor 122 and is monitored through an interface 123 by CPU. The camera is stopped when it comes to a predetermined position, whereby the lateral position of the camera is determined.
In the step S25, the pulses from the encoder representative of the position at which a photograph is taken are counted. The step S26 shows that the printing press starts trial printing. During the trial printing, the "input" button is depressed (Step S27). The rotary encoder 107 is carried by the shaft of the plate cylinder and a counter counts rotation pulses (S28) and in response to a reference signal produced upon one rotation, a counter 123 is cleared. When the number of pulses counted in the step S25 becomes equal to the number of counted pulses from the rotary encoder (Step S29), CPU 206 transmits a signal to a VTR controller 124 so that two VTR1 and VTR2 are activated (Step S30). Next a signal is transmitted to a flash circuit 109 (Step S31) so that the flash lamps 106 are flashed. When one image is picked up, VTRs are stopped.
In the step S32, CPU 206 detects whether the "upper surface display" or "lower surface display" button on the operation board 203 is depressed so that the switching signal is transmitted to the VTR controller 124 (Step S33). Then the signal switching device 125 is activated to select VTR1 or VTR2. In the next step S34, CPU 206 transmits a display signal of a still image to VTR selected by the VTR controller 124 so that the desired image is displayed through the superimposer 205 on the screen of the CRT 204. In the steps S35 - S38, the joy stick is operated so that the cursor is displaced to a predetermined position relative to the image displayed. The joy stick 201 is connected through an interface 202 to the data bus 130 and the cursor is synthesized through the video interface 125 and the superimposer 205 at a position on the screen of the display device 204 corresponding to the position of the joy stick 201.
When the cross-shaped cursor is brought to a desired position (Step S38), the color input button on the panel 203 is depressed so that the position of the coordinates is stored or memorized (Steps S39 and S40). The above-described steps S35 - S40 are repeated for each color and when all colors are entered (Step S41), the upper surface or lower surface image is entered (Steps S32 - S41). Thereafter steps S21 - S41 are repeated for the register mark on the man side.
When all inputs are entered, the operation button is depressed (Step S43) and CPU 206 calculates . registration errors and distance over which the plate cylinders must be shifted (Step S44). They are transmitted through the data bus 121 to the motor drive circuit 12 so that respective registering motors 52-54 are energized (Step S45). In this embodiment, the patterns will never be inputted in inclined direction and the patterns of upper and lower sides are inputted at the same time and position so that the steps 2 (S-2) and 3 (S-3) in FIG. 4 are unnecessary to introduce. CPU monitors through potentiometers 126 - 128 and an interface 129 the rotations of the motors 52 - 54 so that when the plate cylinders are brought to the set position, they are stopped. In order to effect the calculation control by CPU 206, ROM 151 and RAM 152 are connected to the data bus 130.
FIG. 13 shows a specially designed register mark. When the registration is attained, four parallel bars are spaced apart in the circumferential direction from each other by three millimeters. For instance, these parallel bars are black, blue, red and yellow in the order named from the forward to the rearward along the circumferential direction.
Even in the case of misregistration, these bars will not be superimposed one upon another and the sequence of colors will not change because the misregistration in the circumferential direction is only within ±1 mm. Therefore the operator can easily recognize them or distinguish their colors automatically, otherwise a black-and-white camera and display device may be used.
So far the present invention has been described in conjunction with the offset press, but it is to be understood that the present invention may be equally applied to other printing presses such as photogravure presses, typographic printing presses and flexographic presses.
Furthermore, instead of the joy stick, a mouse, a light pen or digitizer may be used and a menu patch may be marked on the operation panel or a display device. In addition, the arithmetic unit may be a special arithmetic circuit incorporating a micro processor and instead of the printer, CRT or LCD may be used.

Claims

1. A registering method for a multicolor printing press comprising the steps of magnifying and displaying a pattern of a printed medium on a display device; entering inputs of the coordinates of positions of each color pattern for a predetermined element of the magnified and displayed image by coordinate input means; determining registration errors between respective colors based on the coordinates of each color position and the magnifying power of the image; calculating quantities required for adjustment of the positions of plate cylinders based on said registration errors; and registering the printing press depending upon the results of this calculation.

2. A registering device for a printing press comprising a pattern input means for inputting a pattern of a printed medium; a display for magnifying and displaying said pattern; means for deriving the coordinates of the positions of a predetermined element for each color within the magnified and displayed image; means for determining registration errors between respective colors from the magnification of the image.displayed on said display and the coordinates of the positions of said predetermined element and calculating quantities required for the adjustment of the positions of plate cylinders; and means for registering the printing press depending upon the results of calculation by said calculating means.

3. A device as set forth in Claim 2 wherein a lens system and a video camera as said pattern input means and a cathode-ray tube as said display are provided.

4. A device as set forth in Claim 2 or 3 wherein said means for deriving the coordinates of a position comprises a light pen.

5. A device as set forth in Claim 2 or 3 wherein a cursor is displaced on the screen of said cathode-ray tube by means of a suitable position coordinate input means, whereby inputting the coordinates of positions.

6. A device as set forth in any of Claims 2 to 5 further comprising means for obtaining quantities required for adjustment of the positions of each color plate cylinder based on the registration errors between respective colors.

7. A device as set forth in any of Claims 2 to 6 wherein a horizontal or vertical line of the image displayed on enlarged scale on the screen of said display device is inputted, whereby the coordinates of said position are corrected.

8. A device as set forth in any of Claims 2 to 7 wherein said display device magnifying and focusing on a screen a light image transmitted through a lens system.

9. A device as set forth in any of Claims 2, 3 and 6 to 8 wherein a transparent digitizer is placed upon the screen of said display device, whereby the coordinates of a position are inputted.

^10. A device as set forth in any of claims 2 to 9 wherein said pattern input means is provided on the printing press so as to input the pattern of a printed medium on the printing press.

11. A registering device as set forth in Claim 10 wherein a video camera or a high-speed video camera is used as means for inputting a pattern; and an image recording device such as VTR (video tape recorder) or a frame memory is provided, whereby a recording mechanism capable of instantaneous pattern recording is provided.

12. A registering device as set forth in Claim 10 or 11 wherein said pattern input means comprises an input means for inputting the coordinates of positions of a predetermined portion of a pattern on a plate to be inputted, a means for displacing input cameras on the printing press and a rotation phase detecting means for detecting the rotation condition of plate cylinders of the printing press, whereby an arbitrary portion on a printed medium can be inputted.

13. A registering device as set forth in Claim 10 wherein said pattern input means is such that a video camera or a high-speed video camera is used in combination with a shutter or a stroboscope to permit an instantaneous exposure to the printed medium running on the printing press, whereby still images are intermittently displayed and consequently one perceives a continuous still image.

14. A device for determining registration errors in a printed medium comprising a display device for magnifying and displaying a pattern of a printed medium, means for deriving the coordinates of a position of a predetermined element for respective colors within the magnified image displayed on said display device, means for determining registration errors between for respective colors from the magnification of the image displayed on said display device and the coordinates of the position of said predetermined element, means for determining the quantities for adjusting the positions of the plate cylinders in response to said registration errors, and means for outputting to display and/or print said quantities for adjusting the positions of the plates.