EP2269824B1 - Method and device for monitoring the registered processing of web-like material in installations - Google Patents

Description

The invention relates to a method and a device for monitoring the fitting processing of web-like materials in installations according to the preamble of claim 1 or according to the preamble of claim 13.

The processing of web-like materials such as printed products is carried out at increasingly higher web speed. In addition to the actual printing process in which, for example, an image is applied, the processing also includes further processing processes such as perforating, stamping, embossing, creasing, painting, etc. in an in-line operation, i. even while the train is running, without the product resting. At the now quite common speeds of 3 m / s and above, the observation of the quality of the printed image with the naked eye is no longer reliably possible.

Thus, web-tracking devices have become commonplace which illuminate the web by means of a stroboscope and produce images therewith. In particular, the use of video cameras can achieve a high quality, still image that allows a very good evaluation of the quality of a print.

In addition to monitoring each of the two printed pages, the monitoring of double-sided printed products often requires an opportunity to observe the position of a printed image on one side in relation to the positioning of a printed image on the other side. Analogously, this applies of course to the same extent for a monitoring of 2 observation points on the same side of a printing line, if for 2 cameras are used or in a correspondingly modified form, even if a single camera takes several places of the printing web and thereby a local assignment must be done in a very precise way.

For this purpose, facilities have become known which make use of the property of transparency, in particular in the case of transparent materials, and make it possible to make both images one above the other superimposed in their relative position by illumination in the back light / transmitted light.

Although this method can ensure a very high accuracy in the reproduction of the positions, it fails completely with opaque material.

In this case, further devices are known in which two cameras are mounted exactly opposite each other and by means of an exactly simultaneous image acquisition two images are generated, which then bring on a screen simultaneously and accurately positioned next to each other or one above the other or in any two windows divided arbitrarily. This allows an operator to recognize the relative positioning of the two images with each other quite accurately. The recognizability and correctness of displayed deviations depends on the equality of the image scale (ZOOM) of the cameras but also on the exact simultaneity of the two images and the accuracy of the mounting of the cameras.

In order to exclude these sources of inaccuracies as far as possible or at least to minimize their influence, often even separate and additional precisely configured camera systems are used.

On the other hand, however, they are extremely expensive, so that it is hardly economically viable for occasional use to purchase such a device.

For a conventional one-sided web observation camera systems with exactly opposite recording devices, however, then only conditionally usable if it is transparent / translucent sheets, since then affect the recording devices in different ways each other.

In the reproducing the preamble of claim 1 and 13 German utility model application DE 200 07 621 The company Drello GmbH is therefore proposed a device that works with two cameras already used for conventional web observation and both with opposite cameras and with cameras that can work with a relative offset to each other. This is achieved by simultaneously displaying one and the same mark on the web on both sides of the captured image. Thus, each camera image contains one and the same reference point, at which the printer can then orient himself in the assessment of a mutual fit of the images applied on different sides.

A disadvantage of this method is that a not very simple additional device must be used and both cameras must be arranged at least so close to each other that the same marking device (there is proposed a laser) still comes to rest in the image field of both cameras. Such an arrangement is often not possible for reasons of web guide in the machine and other mechanical engineering conditions.

It is therefore the object of the invention to provide a method and a device according to claim 1 or according to the preamble of claim 13, with which it is possible for a web observation at two locations or on one side of the material web with commercially available cameras without consuming additional equipment to get along for the function of the system, with the highest possible and sufficient for a controller accuracy in the display and / or assignment of the recorded images should be achievable.

The solution of this object is achieved by the features of claim 1 and 13, respectively.

The dependent claims 2 to 12 or 14 and 15 have advantageous developments of the method and the device according to the invention to the content.

Fig. 1

eine schematisch stark vereinfachte Darstellung einer ersten Ausführungsform einer erfindungsgemäßen Vorrichtung, und

Fig. 2

eine ebenfalls stark vereinfachte schematische Darstellung einer zweiten Ausführungs- form der erfindungsgemäßen Vorrichtung.

In the following, the proposed procedure will be described by way of example on the basis of use in a printing machine, in which a pressure is applied on both sides. Equally, of course, it is also possible to proceed if an already applied pressure exists on one side and processing takes place in the machine in question only on a second side, the result of which is then to be observed in relation to the already existing pressure. This shows:

Fig. 1

a schematically simplified view of a first embodiment of a device according to the invention, and

Fig. 2

a likewise greatly simplified schematic representation of a second embodiment of the device according to the invention.

A video link observation system consisting in each case of an image acquisition module 1 opposite the front of a printed web 7 and an image acquisition module 2 opposite the back side of the same printed web, an adjustment module 14, a synchronization module 10, an image storage module 12, an image evaluation module 15 and display module 13 is installed in the machine (FIG. Fig. 1 ). In this case lie between the place of processing, such as a printing unit, and the location of the installation of an image acquisition module often railway tracks of 20 m and more. The two image acquisition modules, consisting of at least one camera, a lens, an associated illumination, an electronic control unit and possibly adjusting motors and a mechanical device, are designed as a compact assembly. Both image pickup modules can each be moved along a traverse 3, 4 transversely to the web running direction. Furthermore, on a format cylinder 5, 6, ie a cylinder which covers exactly one format length per revolution on its surface (for example a printing form cylinder), a rotary encoder 8 is mounted as a format clock module which generates one format pulse on one revolution generated, which is forwarded to the synchronous module 10. Furthermore, a friction wheel is mounted on the moving web as Bahnwegmessmodul 9, the scope of which rolls passively on the web, travels over a revolution a well-known distance, thereby emits a known number of pulses, which are forwarded as a wegproportionale information to a synchronous module 10 become. It is advantageous for a conversion if the circumference of the friction wheel makes up an integer fraction of a meter.

In the synchronous module 10, the image acquisition times for the two cameras are calculated from the aforementioned incoming information as well as previously known geometric information and / or information entered via the operating module 14, such as the distance between the image acquisition modules 1 and 2 and the thickness of the web material.

To display the front and rear side image, the screen is divided into 2 parts here in the display module 13, with the front side image being shown on one side and the back side image being precisely positioned relative to one another on the other. In the exemplary case, it is first discussed how the image is recorded and displayed in the web running direction exactly aligned.

When installing the two imaging modules 1.2 in the printing press, the distance between the center lines of the camera images is measured by means of a highly accurate scale printed on virtually non-stretchable material of known thickness. This measure is converted to a scale thickness zero, so that in this way the normalized distance between the two camera positions is determined. This measure is entered, for example, via the operating module and stored in the synchronous module. If the system additionally has an image processing module 15, this distance can also be automatically calculated from features of two recorded images of such a scale.

If the friction wheel 9 is located in front of a deflection roller 16 on the inner side of the track, then the distance normalized to zero between the two cameras 1, 2 is equal to the true path traveled by the friction wheel 9. If the friction wheel 9 is mounted on a side opposite to a deflection roller, then this length must be converted accordingly.

The material thickness of the printing substrate is then entered via the input module 14 of the video web monitoring system and the effective distance to be expected of the cameras is calculated by the synchronizing module 10 with the aid of the data for a thickness zero and the thickness information.

With the beginning of printing, the web is conveyed and simultaneously stretched. The length of a format, i. the length, which constitutes exactly one repetition of a pressure, is effected by a revolution of a format cylinder 5, for example of the printing plate cylinder, and therefore also represents the distance between two format pulses (zero momentum) from the rotary encoder 8 mounted there. At the same time, the friction wheel 9 rolls over a certain length, with exactly the length of the printed product stretched at this point passing between 2 format pulses. In this way, the current stretched format length is determined as the rotational path which the friction wheel 9 has covered.

If no first position of a page is previously known, then at a first location, which has been selected by the operator and approached via the adjustment module, a first image is taken from a first side of the path through the associated image acquisition module. This image is stored in the image storage module 12 as a first image. From the above-mentioned data is subsequently calculated by the synchronous module 10 by which distance the to be made on the second side recording of the made on the first page shot has to be made so that it meets exactly the same point of the web, as the first made Picture of the other side of the track. The synchronous module 10 then initiates an image acquisition in the second image acquisition module with a corresponding delay. This image is stored in the image storage module 12 as a second image.

For example, if already known by a previously run print job of the same kind, which positions are and are stored in a job memory 16, a first position is read from the memory and used for a first image pickup device as pre-positioning, while based thereon by means of the abovementioned Method of the moment of recording the second image pickup device is calculated. Likewise, of course, it is possible to proceed from other sources (for example, precursor information) that already know image parts whose positions in the current print are to be compared with one another.

Both stored images are shown by a display module 13, for example, now arranged on the screen that comes exactly to lie in the web running direction in the middle of the screen exactly the center of the two pictures taken in each case. For even more precise observation, a crosshair or another marking can additionally be superimposed by the display module into the image, which can still be advantageously displaced in its position via the operating unit. In any case, the operator can accurately recognize the current mutual position of the machining results on both sides and correct if necessary by intervention.

However, it often happens that such a simple installation of the image pickup devices, as in Fig. 1 has been described is not possible. With the use of pulleys as in the Fig. 2 For example, the configuration shown will require consideration of material thicknesses as well. In the simplest case, this size is determined by the operator via the input module 14 (FIG. Fig.1 ). However, it can also already be stored in the order memory 16 (FIG. Fig. 1 ), and is then transmitted to the synchronous module after reading. Alternatively, a device can be used in which the material is introduced with single or multiple thickness and then determines this size independently.

Another complication in the procedure occurs when the roller 34 ( Fig. 2 ) even takes a considerable torque from the web to their own drive or even driven itself. In this case, it becomes necessary to take into account the uneven web elongation caused thereby at the picking locations thereby caused. For this purpose, two friction wheels 31, 33 are then used, for example, which, as already described above, each determine the different format lengths and transmit them to the synchronization module. The synchronous module then calculates the respective image recording times taking into account the associated path expansions.

In the cases described above, it is also possible to proceed in such a way that the additional corrections which result from material thickness and differences in web stretch do not flow into the calculation of the recording times, but rather send them to an image processing module 15 (FIG. Fig.1 ). This module then takes into account both the material strain differences and the material thickness by means of a corresponding processing of the displayed image by both translating the position translates and at least one of the images of the determined strain corresponding one or two-dimensional compressed or stretched adapted. This method is particularly advantageous when constantly varying expansion ratios set. Furthermore, of course, both methods can also be used in combination, so that, for example, the material thickness and the change in the recording time due to material expansion are taken into account in the calculation of the recording time and only the changes in the geometry of the image resulting from differences in strain are correctively compensated for the representation become.

In the above example, it is assumed that the operator can recognize from a print pattern or other specifications, or knows how the images of the two sides must come to lie to each other, for example, by a pattern that it represents objectively. This pattern can then be interpreted similarly to a setpoint as nominal positioning.

In an additional embodiment, an automatic evaluation of the images in an image processing module added to the system may result in an automatic evaluation Determining the offset in the register of the top and bottom done by a target position with a recorded actual position is compared by a suitable image evaluation and displayed the determined offset displayed or compensated by a control device.

To achieve an easy-to-interpret scale image, it is of great advantage if both cameras have the same magnification (zoom). In an automatic image analysis, this is almost inevitable, if the computational effort is to be kept within limits. This can be achieved, for example, by adjusting the lenses of the cameras via their electronic zoom adjustment to the same values that were previously calibrated precisely using a scale. Likewise, an equal zoom scale can be achieved by using markers of a previously known size applied to the web or out of the web with both cameras for this purpose. A same scale can then be set by the fact that the zoom position of at least one of the two lenses is changed until the markers are imaged in the same size with two recording devices.
The procedure can also be modified such that one of the images for reproduction in the ratio of the measured image sizes measured during the calibration is reduced or enlarged, wherein the image processing module previously makes a corresponding geometric processing such as compression or elongation.
In this case, the magnification of the two recording modules can be determined in that at least one of them receives a pattern of known size and the image scale is determined therefrom in the image evaluation module. Preferably, the magnification of at least one camera is changed until it corresponds to a given imaging scale sufficiently well. Furthermore, both recording modules can use a pattern of known size. Finally, the scale can be arranged outside the material web region, the image acquisition module approaching this position before image acquisition and determining and / or adjusting the image scale. Further, before being displayed on the display module in the image processing module, the images or sub-images may be altered to have the same or different predetermined elongation. Furthermore, it is possible to determine an assignment of two images or partial images by the target result of a subsequent further processing of the processed material web 7.

A further advantageous embodiment, which is based on the use of an additional image processing module 15 (FIG. Fig. 1 ), it allows to save the Reibradanordnung by the format length from the distance of the repetition of two significant areas of the printed periodically repeating print image is determined. Such areas can also be trademarks.

In a further embodiment, the correction of the format length is not taken into account by the fact that this is included in the delay between the recording of the one side and the recording of the second page, but rather the representation of one of the two fields on the monitor by exactly this Amount shifted takes place while the recording always takes place with a constant shift of the image triggering. The determination of the register from front to back is limited in the case of a visual evaluation on the monitor by the resolution of the monitor, i. Only location information with a resolution of 1 pixel can be displayed reliably. Offsetting the correction in the last-mentioned manner is therefore permissible in every case and does not lead to any reduction in the accuracy in the method.

The display of the top and bottom images is done on the same monitor side by side or with each other. For an optimal recognizability of the register offset, both images are displayed in the same magnification.

In addition, a position determined by the printer for the evaluation of the register or also determined, for example, by the method described above under [00025], can be marked in print on an image by displaying a characteristic pixel with the center of a crosshair displayed on the monitor by the display unit Agreement is brought. This marker is superimposed in the second image at the same position and thus serves as a reference for estimating the register offset between top and bottom.

Another possibility for image display is the superposition of a top image with the associated image of the bottom. The mixing ratio of the images can be set, for example by the operator, to an optimum transparency for the visual observation. To improve the visibility of the relative positions of processing results of a machine in the two images or image portions, it may also be advantageous, for example, a cold seal image applied on the back and taken by an image acquisition module in a false color representation relative to a true color print image or another camera image of a processing result display.

With the invention described above, a high-precision cost-effective method for register-accurate imaging of both sides of a two-sided processed web is proposed. It should be pointed out that the processing of the web can not only be a question of printing, but rather also other processing processes that involve leave reproducible result can be observed and evaluated by the method according to the invention.

In addition to the above written disclosure of the invention is hereby supplementing the same explicitly to the drawings of the invention in the Fig. 1 and 2 Referenced.

LIST OF REFERENCE NUMBERS

1.2

Image Capture Module

3.4

traverse

5.6

format cylinder

7

Processed railway / material web

8th

Format clock module

9

Bahnwegmessmodul

10

synchronous module

12

Picture memory module

13

display module

14

adjustment module

15

Image processing module

16

Job memory module

31.33

friction wheels

34

roller

Claims (15)

1. Method for monitoring the register-true processing of a material web (7) in industrial plants, comprising the following method steps:

   - processing of the material web (7) at a first point;

   - independent processing of the material web (7) at a second point, wherein the processing at the two points respectively leaves an identifiable structure which recurs periodically at a fixed spacing;

   - arrangement of image-recording sites at positions which have a preset fixed geometric spacing; characterized by the following method steps:

   - recording of a number of pulses per periodically recurring structure,

   - recording of signals proportional to the web travel of the material web (7) at the image-recording site;

   - computation of the true structural length from the signals proportional to the web travel and from the pulse signals per periodic structure;

   - computation of the times for the image recording from the true structural length and from the pulse signals per periodic structure;

   - recording and storage of a first image of the first point at the first image-recording site at a first time;

   - recording and storage of a second image of the second point at the second image-recording site at a second, later time; and

   - simultaneous displaying of the first and second image.
2. Method according to Claim 1, in which, in an image processing step, at least one of the recorded images or a part thereof is scanned for a recurring detail in the applied structure and a signal is respectively generated at the time of the recurrence.
3. Method according to Claim 2, wherein, as the recurring structure, a marking is applied.
4. Method according to one of Claims 1 to 3, in which the recording time of the second image recording of the second point for each recording is derived from the geometric spacing and the computed true format length at the image recording site.
5. Method according to one of Claims 1 to 4, in which the recording time of the second image recording of the second point is derived only from the geometric spacing and, in the image reproduction, the recorded second image of the second point is represented, by means of calculation methods, translationally displaced by a measure which is calculated from the true structural length.
6. Method according to one of Claims 1 to 5, in which the thickness of the printed material is established and this established value is taken into account in the calculation of the time with respect to the triggering of the image recording.
7. Method according to one of Claims 1 to 6, in which the two images to be recorded and represented are situated at points on the web which are different in the peripheral direction and/or in the direction perpendicular to the web running direction.
8. Method according to one of Claims 1 to 7, in which the image recording is effected with an imaging scale which is not equal to a desired imaging scale, and the recorded image, prior to its display, is converted insofar as the representation is made on the desired imaging scale.
9. Method according to one of Claims 1 to 8, in which a desired recording position of the first point is determined from known digital prepress data, and a desired position of the second point is precalculated therefrom, already prior to the start of a first processing, with due regard to the geometric conditions, in particular the web travel, the imaging scale and the material thickness.
10. Method according to one of Claims 1 to 9, in which optionally selected or predetermined image positions are represented in a preset arrangement to one another, wherein the preset is effected by manual selection or, by virtue of an image processing step, a precalculation is made on the basis of digital image data and these image data are automatically generated from the prepress or from recorded images, wherein the imaging scale and/or the zoom setting of image recording optics is preferably determined from known digital prepress data and from the geometric resolution which is necessary for an analysis of the image parts to be compared.
11. Method according to one of Claims 1 to 10, wherein at least one of the images is reproduced with altered colour.
12. Method according to one of Claims 1 to 11, in which at least a part of all established data and/or images is filed in a job memory and is fully or partially recallable and adjustable at a later time.
13. Device for monitoring the register-true processing of a material web (7) in industrial plants, wherein the processing at two points on the material web (7) respectively leaves an identifiable structure which recurs periodically at a fixed spacing:

    - having a first image-recording module (1) directed at the material web (7);

    - having a second image-recording module (2) directed at the material web (7);

    - having a synchronizer module (10), which determines the time of the image recording of the first and second image recording modules (1 and 2) and respectively triggers the image recordings by the image recording modules (1 and 2);

    - having a format clock module (8), which delivers to the synchronizer module (10) an integral number of structural pulse signals per periodic structure;

    - having at least one image storage module (10), which is in signal connection with the image recording modules (1, 2),

    - having a display module (13) for the realistic display of the images recorded by the image recording modules (1, 2), and

    - having a control module (14),
    characterized

    - in that the two image recording modules (1, 2), viewed in the web running direction (R) of the material web (7), are arranged at a fixed geometric distance apart;

    - in that at least one web travel measuring module (9) is provided, which module records signals proportional to the web travel at the site of the recording of the image, wherein, in the synchronizer module (10) and/or the image recording module (1, 2), the true structural length is calculated from the signals proportional to the web travel and from the structural pulse signals, and wherein the time for the image recording is calculated from the true structural length and from the structural pulse signals by the synchronizer module (10) and, following recording of a first image at the first point on the material web (7) at a first time, and following recording of a second image at the second point on the material web (7) after a later, second time, the display module (13) displays the first and second image simultaneously.
14. Device according to Claim 13, characterized in that the format clock module (8) has a pulse generator, which is fixedly coupled to a formatted format cylinder (5).
15. Device according to Claim 13 or 14, characterized by an image processing module (15) and/or a job storage module (16).

Images