EP1958773B1 - Method and device for checking a printed picture - Google Patents

Abstract

The method involves rendering an image recorded by a video camera (4) on a monitor (5) and comparing the image with an overview screen. A cursor (1b) to be checked is selected at the screen by a control device. The camera is operated in a corresponding position over a real print image by coupling with a control unit (2). The cursor is extended at the screen by an extension device to check the cursor and adjusted correspondingly together with a zoom of the camera by coupling the cursor with the zoom such that the cursor is rendered in a same extension in the monitor during recording. An independent claim is also included for a device for executing a method for checking a print image on a continuous material path by a video camera.

Description

When monitoring a printing web with a video camera, the operator must perform checks on the print image made by the printing press by taking snapshots from the running web using the video camera and controlling the print quality from these recordings. Since areas of a printed image or motif on a moving web can vary depending on the respective position on the printing web, it is necessary to control, for example, the left side of the printed image and then the right side again. For example, when printing stamps, a sheet of approximately 50 stamps is printed in length and width, whereby the print quality of a single stamp at about the left edge of the print image and the print quality of a single stamp on the right edge of the print image must be checked.

It is known to provide an overview image on a screen that displays a virtual print image. In order to select a specific area of the real print image for the check, a cursor, for example a rectangle, is navigated on the screen to a specific area of the overview image, whereby the navigation of the cursor simultaneously moves the camera over the print path accordingly. When the cursor has reached the desired position on the overview image and the camera has also been moved to this location, the actual print image is taken and then the recording is used to check whether the reproduction of the desired area shows a magnification sufficient for the examination. If not, the zoom of the camera must be changed, followed by another shot and determined by this new recording, if the print image in the desired area is sufficiently clearly reproduced.

This method is by repeated readjustment of the zoom and multiple takes on the printed image time-consuming, since it must be waited before each shot until the desired part of the print image is back in front of the camera.

A method for checking a print image is also from the document US 4,736,680 known.

The object of the invention is to provide a method and a device so that in the shortest possible time that region of the printed image can be selected, which is then to be checked.

In accordance with the invention, this is essentially achieved by not only navigating the cursor to a specific position on the overview image at which a check of the printed image is to be made, but also by simultaneously making a magnification change on the virtual overview image such that the selected region of the printed image is also reproduced in the desired magnification on the overview image itself, so the overview image exactly that area of the print image with the desired magnification reproduces without delay, which is then to be checked on the real print image. The magnification setting on the virtual overview image simultaneously changes the optical zoom of the camera according to the setting on the overview image, so that both the position and the zoom of the camera over the current print image are adjusted based on the setting on the overview image. By parameters of the printing press such as rotary pulse generator on the printing cylinder, pulses as a function of the length and width of the printed image and the like can be determined by a computing device, at which time the selected on the overview image area of the print image appears in front of the camera, so in the calculated time, the camera takes a flash photograph of the real print image in the form as it was predefined on the virtual overview image.

This makes it possible for a machine operator to check in a short time exactly the area of a printed image, which he has selected for a review of the print quality, with no adjustment of the zoom on the camera and no repeated recordings are required.

Fig. 1

schematisch ein Blockschaltbild der Vorrichtung zur Durchführung des Verfahrens,

Fig. 2

schematisch ein Übersichtsbild und ein reales Druckbild, und

Fig. 3

ein Übersichtsbild mit einem vergrößerten, ausgewählten Bereich.

The invention will be explained in more detail for example with reference to the drawing. Show it

Fig. 1

2 is a schematic block diagram of the device for carrying out the method.

Fig. 2

schematically an overview image and a real printed image, and

Fig. 3

an overview picture with an enlarged, selected area.

In Fig. 1 1 denotes a monitor which reproduces an overview image of the print image to be produced and an area of the overview image on its screen 1a by means of a cursor 1b can be selected. 2 denotes a control and computing unit connected to the monitor 1, which controls a video camera 4 via a line 3, which is arranged above or in front of a running printing or material web 6 in order to record a printed image 9 (FIG. Fig. 2b ) printed on the web 6 by a printing cylinder 7a. At the pressure cylinder 7 a sensors such. B. a rotary encoder 7 is provided which give signals via a line 8 to the control and processing unit 2.

With 5 another monitor is designated, which is connected to the camera 4 and a shot of the printed image reproduced 9, which was taken by the camera 4. 4a denotes a temporary storage in which the recording of the printed image generated by the camera 4 can be stored.

Fig. 2a schematically shows a virtual overview image 10, which is displayed on the monitor 1 or a touch screen and the real printed image 9 on the printed material web 6 corresponds.

The overview image 10 on the monitor 1 shows a high-resolution virtual image of the print image 9. This virtual image can be obtained in various ways, for example as a pre-press pdf or bitmap (design area). The picture can also be provided by any camera.

Fig. 2b schematically shows the real printed image 9 on the printed material web 6, wherein on the web 6 successively printed images 9 are printed by the printing cylinder 7a. By an arrow, the direction of movement of the web 6 is indicated.

By means of a control device (not shown), for example a mouse, the cursor 1b can be navigated to a specific area of the overview image 10, which is then to be checked for its print quality on the real print image 9. According to the embodiment Fig. 2a For example, the cursor 1b is displaced into the upper right corner of the overview image 10, whereby the image recording position of the camera 4 over the web 6 in the corresponding area 9a on the real printed image is simultaneously controlled by the control and computing unit 2 connected to the control device, for example mouse 9, as indicated by dashed lines at 9a in FIG Fig. 2b is reproduced.

The camera 4 can be moved on a moving device, not shown, transversely to the moving material web, because the web width is often greater than the field of view of the camera. By selecting the image pickup position on the overview image, the camera on the shuttle is simultaneously moved to the corresponding image pickup position.

Due to the known size of the real printed image 9 on the web 6 in terms of width and length and by rotary encoder 7 on the printing cylinder 7a or other sensors, the control and processing unit 2 receives the parameters from which calculates the position of the camera 4 in relation to the real printed image 9 which corresponds to the position of the cursor 1b on the overview image 10. From the given parameters of the printing machine on the one hand and the dimensions of the printed image 9 on the web 6 on the other hand, the control and computing unit 2 can also specify when the real print image 9 appears in front of the camera 4, so that a flash photography of the camera 4 triggered exactly at the time in which the selected area 9a of the real printed image 9 appears in front of the camera 4.

After a recording of the area 9a has been made, the machine operator on the other monitor 5, the recording of the printed image area 9a, which is stored in the buffer 4a, take a look, said in the previous method, the first on acquisition, as a rule, the area to be checked 9a does not reproduce in the clarity and magnification required for optical inspection. Therefore, in the previous method, the zoom of the camera 4 is subsequently adjusted so that the area to be checked 9a can be recorded more clearly and magnified by the camera 4, whereupon again taken a record of this area 9a and then determined on the basis of the new acquisition, whether the reproduction of the area 9a is sufficient for a check of the print quality. If necessary, a further change of the zoom must be made and a further picture taken to obtain on the monitor 5 an image of the area to be checked 9a, which sufficiently clearly reproduces this area for checking the print quality.

According to the invention by the cursor 1b in Fig. 2a selected range of the overview image 10 on the overview image itself by a magnification switch 1 c set to the desired magnification, which appears to be useful for checking the print quality. At the in Fig. 3 In the exemplary embodiment shown, the area selected on the overview image 10 by the cursor 1b is enlarged in such a way that it covers the entire area Screen 1a of the monitor 1 assumes, this enlarged view in Fig. 3 designated 10b. As an example, the overview image 10 in FIG Fig. 2a represent a printed image of a stamp block block to be produced, the stamp block z. B. 50 stamps in width and 50 stamps in the length of the real printed image 9 includes. The area selected by the cursor 1b in FIG Fig. 2a includes, for example, a single stamp in the upper right corner of the overview image 10, wherein by the magnification switch 1 c an enlargement of this single stamp is carried out so that it occupies the entire area of the screen 1a, as Fig. 3 at 10b shows.

By enlarging the selected area 1b on the overview image 10 by means of the magnification switch 1c, the zoom of the camera 4 is simultaneously adjusted by the control and arithmetic unit 2 via a line 3a by coupling the magnification switch 1c with the control device 2 in such a way that during a subsequent recording of the selected area 9a on the real printed image 9 by the camera 4, this appears on the monitor 5 in the same magnification as 10b set on the monitor 1.

The length of the printed image 9 or a corresponding motif on the web 6 can correspond, for example, to 600 pulses of an angular momentum transmitter 7. In the same way, the width of the printed image 9 can be reproduced by an absolute or linear encoder. These parameters are entered into the control and computing device 2 and stored, so that in conjunction with the rotational speed of the printing cylinder 7a, the position of the printed image 9 and the selected area 9a in front of the camera 4 can be calculated exactly.

Instead of a rotary encoder, marks on the printing cylinder can be scanned and other sensors such as inductive sensors and the like can be used to obtain the necessary parameters for the control of the camera positioning.

While the desired detail 1b is selected on the overview image 10 and reproduced in the corresponding magnification 10b on the monitor 1 ( Fig. 2a and 3 ), the camera 4 is also adjusted by position and zoom by the control and processing unit 2 so that in the next step exactly at the time camera 4 can be triggered, in which the selected section 9a of the real print image 9 appears in front of the camera , whereupon the corresponding section 9a of the printed image 9 on the surveillance monitor 5 in the same Playback appears like he is on the overview picture 10b in Fig. 3 previously set.

Instead of a magnification switch 1c, for example, a screen may be provided in the form of a touch screen, so that by tapping the selected area continuously enlargement of the overview image 10 while adjusting the zoom on the camera 4 is made, whereupon after reaching the desired magnification touch the touch Screens finished and thus the magnification on the screen 1a and the zoom setting on the camera 4 is set.

Expediently, a reduction switch 1d for reducing the selected area 10b on the overview image is also provided on the monitor 1, so that it is possible, for example, to reduce the magnification on the overview image and thus the zoom of the camera from too great a magnification.

The enlargement of the selected section 1b on the overview image 10 and thus the adjustment of the zoom on the camera 4 is preferably continuously changed. But it is also possible to make a gradual change in the magnification and the zoom, whereby the steps set in the software are chosen to be correspondingly small, so that a desired magnification can be set.

Instead of a reduction switch 1 b, a switch or a pushbutton can also be provided, by means of which the selected enlargement can be applied to the original overview image 10 (FIG. Fig. 2a ) is reduced, which does not reflect magnification, whereupon starting from the overview image 10, an enlargement of a certain range can be made.

The software required for continuous or small-scale enlargement of a selected area on the overview image 10 is known per se. The control signals of the software used for enlarging the section 1b on the overview image 10 are also used for the adjustment of the zoom on the camera 4 and forwarded by the control device 2 via the line 3a to the camera.

Instead of two monitors 1 and 5, only a single monitor can be provided on which the virtual overview image 10 and by switching the shot of the real print image 9 can be reproduced, the enlargement of a selected area 1b on the virtual overview image 10 in the same way by coupling with the control device 2 results in a zoom adjustment on the camera 4, as previously described.

In practice, it happens that the overview image. 10, for example, has a dimension of 150 x 150 mm and the printed image 9 has a width of about 2.5 m. In such a case, if the machine operator, for example, the print quality in the upper right corner at 9a ( Fig. 2b ) on the real print image, the lower left corner of the print image wants to check for print quality, he can move quickly by means of the cursor on the overview image in the area bottom left of the screen, while the tracking of the camera including zoom setting takes a certain amount of time. In order to bridge this adjustment time of the mechanism or the camera, the corresponding area of the virtual print image from the memory in the selected magnification on the monitor 5 is displayed according to a further aspect of the invention by navigating the cursor on the overview image in the lower left corner so the machine operator immediately sees if he has activated the desired area of the printed image. As soon as the camera then moves into this recording position at the lower left area of the real printed image and at the same time the zoom is adjusted, a snapshot can be taken as soon as the real print image appears in front of the camera, which is then reproduced on the monitor 5 instead of the virtual printed image area , In such a case, it is indicated on the monitor 5 whether the virtual print image or even the real print image is still being reproduced. Ideally, ie with high print quality of the real print image, the reproduction of the real print image on the monitor 5 would not differ from the virtual print image previously fetched from the memory in the selected area at the selected zoom.

In this way, regions of a large print image that are further apart can also be checked quickly, because by the reproduction of the selected region of the virtual print image during the travel time of the camera, the machine operator can already check on the monitor 5 whether the selected region is also the one he is wants to examine, and whether this selected area is displayed in the magnification chosen by him or not, whereupon on the magnification switch 1c a zoom change still on the virtual Print image can be made until the camera is moved to the appropriate shooting area and records the real image in the selected area in the selected magnification so that it can be played on the monitor 5.

Claims (4)

1. Method for monitoring a printed image (9) on a moving material web (6) by means of a camera (4),
   wherein the image recorded by the camera is reproduced on a monitor (5) and compared with a predetermined overview image (10),
   at the overview image (10), a partial area (1b) to be inspected is selected by means of a control device and, by coupling to a control unit (2) connected to the camera (4), the camera is simultaneously moved over the real printed image (9) into the corresponding position,
   characterised in that
   at the overview image (10), the selected partial area (1b) is enlarged by an enlarging means (1c) for carrying out the inspection, and simultaneously, by means of coupling to the zoom of the camera (4), the zoom of the camera is correspondingly moved so that in the following photograph of the real printed image (9) by the camera (4), the partial area (9a) of the printed image is reproduced in the same enlargement at the monitor as was previously set at the overview image (10).
2. Method according to claim 1,
   wherein two separate monitors (1, 5) are used for reproducing the overview image and reproducing the photograph of the printed image (9) by the camera (4).
3. Method according to claim 1, wherein a single monitor is used for reproducing the overview image (10) and for reproducing the photograph of the printed image (9) by the camera (4), and switching is performed between the overview image and the photograph of the printed image at the monitor.
4. A device for performing the method of claim 1, wherein an enlarging means (1c) for enlarging a partial area of the predetermined virtual overview image (10) is coupled to the zoom of the camera (4) via a control unit (2) such that the performing of an enlargement of a partial area at the overview image leads to a corresponding movement of the zoom at the camera (4).

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