WO1996030733A1

WO1996030733A1 - Process for checking colour print original copies and device for carrying out this process

Info

Publication number: WO1996030733A1
Application number: PCT/DE1996/000593
Authority: WO
Inventors: Fritz Kurandt
Original assignee: System Kurandt Gmbh
Priority date: 1995-03-30
Filing date: 1996-03-26
Publication date: 1996-10-03
Also published as: DE19511782C2; JPH11502924A; EP0817955A1; DE19511782A1

Abstract

The invention concerns a process for checking colour print original copies for correctness and/or accuracy of colouring, alignment, printed image arrangement and the like in the high-speed on-line production of packaging, labelling and comparable mass products. A plurality of production steps are to be performed on different mechanical units whose sequences are controlled by predetermined codes. A plurality of sequentially controlled semiconductor radiation sources (1) of different spectral regions are used. The reflected portion of the radiation focused on the codes of the test sample controls subsequent processing operations via a computer-controlled electronic evaluation system. The semiconductor radiation sources are disposed in a linear and/or monoplanar manner and are controlled sequentially and in a pulsed manner according to their spectral region. The portion of radiation returned by the test sample is projected in the correct position via a receiver lens system onto a CCD receiver and the intensity patterns supplied by the CCD receiver are evaluated by an evaluation system.

Description

Process for testing color printing templates and device for carrying out the process

The invention relates to a method for checking color printing templates for their correctness and / or accuracy with regard to coloring, alignment, printed image arrangement and the like according to the preamble of claim 1 and to a device for carrying out the method.

A device for carrying out such a method is already known from EP 0 256970 B1. This known device for color measurement on a sample with a transmitter focusing a plurality of semiconductor radiation sources of different spectral ranges controls the radiation sources sequentially, the radiation reflected by the sample being fed to a computer for evaluation by means of a single receiver and the Radiation sources are focused on the sample in such a way that the sequential control of three semiconductor radiation sources for the colors blue, green and red is aimed at one and the same point of the sample.

The known device is used in the

Monitoring of automated manufacturing processes in which codes are printed on the products to be manufactured or processed, by means of which the manufacturing process can be controlled. A preferred application example for such a test method is the fully automated production of folding boxes as packaging for a wide variety of products, such as the pharmaceutical industry, the food industry and the like. Here, the sequence of the individual processing stages is broadly characterized in that initially large-format cardboard sheets are provided with colored imprints, the arrangement and outline of which are matched to later folding boxes, of which a single cardboard sheet can contain a large number. The print images are in

Depending on the format size of the folding cartons to be produced, the areal cheapest arrangement for minimizing waste is distributed in such a way that a maximum of individual cuts can be produced from standardized sheet formats. It is possible that the later individual cutouts, in technical terms here referred to as "benefits", are printed on the sheets in very different orientations, for example rotated in rows and rows by 90 ° or 180 °. A wide variety of imprints, for example for folding boxes of different sizes or different products, can also appear on one and the same sheet and the sheets alternately have different total prints. The stacks are delivered in large pallets matted cardboard sheets with the color imprints, individually removed from a so-called insertion, for example by means of suction cups, and separated in cycles, fed to snow-punching punching machines, which then punch out the individual benefits precisely from the sheet. This results in the desired flat individual blanks, which initially remain in a loose bond in the cardboard sheet, in order to be separated in a subsequent operation in a stripping station, and then to be fed to further folding, adhesive and similar stations in a selected manner.

With such an online production, in which up to 10,000 sheets per hour are processed on modern high-performance machines, i.e. so with one

Cycle sequence of about 2.7 / s, several automatic controls have to be installed along the production line in order to be able to recognize rejects or other errors in the production process without delay and to intervene. The speed of control over the human eye would not only be personnel-intensive here, but would also be essentially impossible because of the production speed, which is no longer visually traceable.

In the selected exemplary embodiment, there is a critical control station between the input-side pallet feed, especially in the area of a so-called feed table, after the cardboard sheets have been separated and before they are introduced into the punching station. The cardboard sheets individually removed from the sheet stack via the suction cups are in this case transported from the insert via transport belts to the feed table and both against a front stop which is referred to as the front mark, as well as precisely aligned against a lateral stop, the so-called side mark. Positioned in this way, the cardboard sheet stands still for a short time (approx. 10 ms) before it is introduced into the punching station, that is, at the moment in which the front and side edges are positioned extremely precisely. Then a starting chain and gripper system takes over the sheet or blank and pulls it into the punching station, which in the given high-performance production takes place in rapid succession for all subsequent sheets in the same way. Within the punching station, the chains moving the blank there are slowed down again with exact timing and stride length. The subsequent stamping stroke of the stamping unit separates the folding box blanks in the given cycle sequence, which here is less than 3 / ε.

Before the color printing sheets are introduced into the punching station, they must be checked for a plurality of individual criteria in order subsequently to be able to avoid rejects as far as possible. This includes recognizing that the correct sheet in accordance with the die and patrix of the punch has been aligned on the feed table in front of the punching station, especially since the intermixing of different color printing templates, that is to say of cardboard sheets with different printing contents, is by no means excluded when delivering pallets can be. As is known per se, this type of security is checked by means of binary code printed on the sheets. A further control criterion is that of the sheet being inserted in the correct direction, that is to say its alignment on the attachment corresponding to the subsequent punching process. location table. It must also be checked that the print image (s) are properly aligned with the sheet.

From the field of printing technology, it is known to use so-called print registers, which later are preferably register triangles located in the area of the waste edges, the scanning widths and color contents of which have to be checked via an actual / setpoint comparison. Finally, an essential control criterion is the check for color fastness of the color printing template for each of the printing inks used.

In the past, this majority of the test procedures containing the most varied parameters had led to the most varied of solutions and suggestions. Initially, it was obvious to use color video cameras, that is to say the recording of all test criteria with a single detector condition. However, this showed the difficulty that, given the television standard of 50 fields per second specified by the industry, only one field requires a standstill time of 20 ms after exact positioning on the feed table, the evaluation time over the Computer electronics still has to be added, since it is only then decided whether the criteria mentioned above for the subsequent scrap-free punching process are fulfilled in their entirety. Such long downtimes cannot be tolerated with online production on modern high-performance machines, they would significantly reduce the required product output per unit of time. But also installation difficulties, not least in the required precise camera positioning and vibration-free fastening, as well as the separate attachment of additional lighting sources, make monitoring using color video cameras unrealistic.

An improved control option is the use of so-called print mark scanning, by printing additional individual characters on the color printing templates by means of optical fiber sensors, the existing coded printing can be recognized very quickly, so that in the event of malfunctions, the automatic machine sequence is stopped and the faulty cardboard sheet before it enters the punching crucible is drawn in, can be removed. However, it has been shown that the control options realized by means of optical fiber sensors do not provide an adequate optical resolution for the constantly growing requirements and, in particular, cannot be used for checking the necessary color measurements.

The above-mentioned device for color measurement according to EP 0 256 970 B1 already largely remedies this, since it contains a color measuring head, whose punctiform scanning is possible with a high resolution and which also works with a high measuring sequence. This device for color measurement is equipped with three semiconductor radiation sources of different spectral ranges, namely for the colors blue, green and red, which are triggered in series by pulses. The radiation focused on a point reflects the remitted portion from this point back to a single receiver, which is followed by a computer and evaluation electronics. With this device the measuring process is only possible with moving color printing originals, the movement being measured by means of an incremental encoder in given path units. However, if the measurement is not made in the resting phase but in the movement, that is to say here when the color printing template is moved from the feed table to the punching station, then this means that defective sheet templates are recognized and corresponding false signals can be evaluated , however, the subsequent production step can no longer be stopped, so that the

Punching process is still running. The result is a time-consuming removal of the mispunched individual benefits from the interrupted production process by hand, that is to say a considerable loss of time.

This is where the present invention comes in, which is based on the task in general, for high-speed production systems, the production processes of which are automated, wherever false / directional checks can only be carried out on samples which are temporarily stationary, and with downtimes in the range of a few milliseconds, to be able to check for a number of different parameters, such as the colors, for example.

This object is achieved according to the invention by the features specified in the characterizing part of claim 1.

Advantageous refinements and developments of this task solution result from the subclaims.

Because preferably three semiconductors emitting different wavelengths or spectral ranges If the light sources are arranged and controlled in a line or area in such a way that color printing originals are sequentially and monochromatically irradiated line or area, line and area color coding can be easily detected and analyzed with a high resolution. The reduction in line or size ¬ Trix-like arrangement of the large number of different semiconductor light sources via suitable optics and the projection of the reduced reflection image onto CCD receiver elements ensures an integrated structure of a device unit suitable for carrying out the method with relatively robust, service-friendly conditions. The use of CCDs as electronic image converters, ie components that are almost unrivaled today, is possible here in a particularly advantageous manner even with a high storage capacity, the CCD receiver being able to be cost-effective since it only receives monochromatic light. Since the individual receiving elements (pixels) are arranged with high accuracy in a fixed spacing grid, this grid can be used for geometric measurements, ie the measurements can be carried out with good resolution based on the geometric assignment between the illuminated line / surface and the receiver.

So far, CCD sensors have often been used in conjunction with flash lamps, or halogen light has been used without pulsing, with color components having to be separated by filters in front of the receivers. Wherever codes are removed from a template using a scanner and processed in a computer-controlled manner, for example when cashing out goods in wholesale stores, the one to be scanned can and will be The original is illuminated only in a non-pulsed manner with monochromatic constant light sources so that, for example, when red light sources are used, color detections which lie in this wavelength range cannot be carried out. Here, too, it is an advantage of the procedure according to the invention to remedy the situation, that is, to be able to analyze each color area separately. The present method can be combined into a functional unit, which considerably simplifies assembly, disassembly and maintenance. The measurement of extremely short rest positions in extremely high production processes, i.e. during a sample standstill of only a few milliseconds, makes the present method interesting for a wide range of applications. Passer triangles known from printing technology can now also be checked for their color content.

The present method is to be explained in more detail with the aid of the accompanying drawings. Here mean:

1 shows a schematic illustration of only a row of semiconductor radiation elements which are arranged cyclically in a repetitive manner and sequentially emit light of the wavelengths blue, green and red with the associated collecting optics, and

FIG. 2 shows an illustration according to FIG. 1 with reduction optics for the light remitted by the sample onto a CCD cell receiver. The dimensional arrangement shown in the exemplary embodiment according to FIGS. 1 and 2 for carrying out the method according to the invention consists of a row 1 of five times three semiconductor radiation sources, each triple periodicity each having a blue, green and red light-emitting semiconductor diode la, lb, lc. This periodicity is repeated a total of five times in the row shown, ie the blue semiconductor diode la, the green semiconductor diode lb and the red semiconductor diode lc are followed again in this order by la blue, lb green, lc red in a cyclical order. The semiconductor diodes la, lb, lc as radiation sources are connected to a control unit which carries out a serial control. The serially controlled semiconductor radiation sources, that is to say briefly emitting light pulses in succession, in each case together, but in succession the blue, green and red, are identified by a suitable mirror and lens arrangement 2 as a blue, green and red line 3, that is to say as a projected projection, the semiconductor arrangement is projected directly onto the test specimen, that is to say onto the bar and / or area coding printed on the test specimen, as a print mark (s).

In the simplest case, the light line 3 (or light matrix) generated is carried out using a series of red, green, blue light-emitting diode blocks, which is collected by a cylindrical lens 2. The linear blue, green and red semiconductor arrangement projects red, green and blue lines with a length of 100 mm in the exemplary embodiment, ie on a 1: 1 scale of the diode arrangement. The light reflected or remitted by the projection surface is then, as shown in FIG. 2, via a converging optics 4 again sharp image in the form of line 5 in a dimension reduced ten times. A 10 mm long CCD receiver is arranged in the imaging plane of line 5. In the exemplary embodiment, the CCD receiver is composed of 1,000 pixels, that is to say receiver elements with a center spacing of 10 μm, that is to say that for each 0.1 mm of the illuminated line on the test specimen, one pixel is used as a measuring sensor and thus also one geometric assignment is possible with accurate measurements.

The simplified representation according to FIGS. 1 and 2 thus represents a line camera with one-dimensional scanning in its mode of operation and application, whereby it is easily possible and within the scope of the present inventive concept to arrange this one-dimensional arrangement as a matrix into one expand two-dimensional geometrical arrangement, with the color sequence then blue, green, red; blue, green, red etc. are repeated in a row for the second dimension in the respective column, i.e. in the first column again starting with blue, green, red, in the second with green, red, blue in the third with red, green, blue and so on, cyclically permeated with the given periodicity.

Because the individual receiving elements are positioned with high accuracy in a fixed spacing grid of 10 μm here, this grid can be used completely for geometric measurements, for which only the length of the light line 3, the imaging scale of the receiver optics 2 and thus ultimately the Dimensioning of the CCD receiver and the number of receiver elements must be known. The light-emitting diode combinations 1, which are driven in series in rapid succession, thus generate, on the CCD receiver elements, geometrically, at the same location, reception signals which correspond to the remitted light components of the red, blue and green projection lines 3.

The CCD receiver elements are followed by a computer-controlled evaluation device which evaluates the intensity pattern supplied by the receiver elements in the three different spectral ranges with regard to the geometry in relation to the print marks on the test specimen irradiated by the semiconductor radiation sources and with regard to the color to be derived from the intensity pattern .

The method according to the invention and the mode of operation of the device described above are to be explained with reference to a folding box punching machine which, as described above, punches out the folding box blanks from cardboard sheets aligned for the punching process. Codings and print marks are applied to the cardboard sheets as templates, which must be recognized as correct, otherwise the punching process is interrupted. Before the punching process begins, the CCD receiver is calibrated against a white standard, ie the reflectance of the white standard is measured when irradiated with the different wavelengths, and the activation times of the radiation sources and thus the exposure time of the receiver elements controlled depending on the spectral ranges so that the same reflectance, for example 100%, is generated in each spectral range. Then the individual markings to be recognized are irradiated and the respective intensity pattern generated by the CCD receiver depending on the location as. Comparison patterns are stored or the intensity patterns are analyzed with regard to color and geometry and comparison values are saved.

Then the actual test procedure begins, i.e. Before each punching process during the very short resting position of the cardboard sheet, the control unit switches on the red, green and blue radiation sources in quick succession and thus exposes the CCD line, on the surface of which the pattern of the detected original is shown. With each exposure process, the amount of light supplied to the pixels is integrated and serially read out and evaluated pixel by pixel for evaluation. The evaluation device is thus aware of which measurement point on the template with which intensity was emitted during the respective red, green or blue exposure and can make a comparison with the specified intensity pattern and make a statement about the correctness of the color or the location of the Hit print template.

This arrangement can thus recognize both line codes, such as EAN codes, as well as area codes, such as the registration triangles, as used in printing technology, in color and evaluate them with the computer-controlled evaluation electronics. If the color or the position of the detected coding or brand does not correspond to the respectively given template, the punching process can be stopped, the cardboard sheet removed or adjustments made and then continued. In a further exemplary embodiment, not shown, the semiconductor radiation sources in each case of a spectral range can be arranged in a row for themselves, so that, for example, a row with red, a row with green and a row with blue semiconductor radiation sources are provided, the radiation of the different rows, however, should form projection lines 3 which lie one above the other. The radiation of different spectral ranges can preferably be combined via dirchroic mirrors, which makes the measurement even more precise, ie any position-dependent position errors are not included in the measurement, since they are the same for all spectral ranges.

Furthermore, the arrangement of the semiconductor radiation sources can be carried out in such a way that radiation sources with two alternating spectral ranges, for example red and green in a first

Row, and radiation sources with yet another spectral range, for example blue in a second row, are arranged, with both rows emitting a line from the side. Here, too, the radiations can be brought together via dichroic mirrors.

However, other linear and flat arrangements of the semiconductor radiation sources are also conceivable. Hybrids can also be used in which semiconductor elements of different spectral ranges are arranged in one housing. It is essential that the remitted light line or light surface is mapped on the CCD receiver in a geometric assignment is so that a correct evaluation can be made.

In the exemplary embodiments, radiation sources with three different spectral ranges have been selected; Of course, several or other spectral ranges can also be provided.

Claims

claims

1. Method for testing color printing originals for their correctness and / or accuracy with regard to coloring, alignment, arrangement of printed images and the like, in the high-speed online production of packaging, labeling and comparable mass products, in which a multitude of Go through production stages on different machine units and are controlled here by means of codings which can be predetermined on the test specimen, using a plurality of sequentially controlled semiconductor radiation sources of different spectral ranges, the reflected radiation component exceeding the radiation focused on the codings of the test specimen a computer-controlled evaluation electronics controls subsequent processing operations, characterized in that the semiconductor radiation sources are arranged in a line or flat shape in such a way that, when sequentially activated, those on the color printing originals are in the form of a line sequence The encodings provided and / or geometric surfaces are irradiated in lines and / or areas mono-chromatically in different spectral ranges in pulses that the remitted radiation component via a receiver optics as a visual image on a CCD receiver with a large number CCD elements are projected in a geometrical assignment and that by means of the screening of the elements depending on the imaging scale of the receiver optics and the number of elements, the geometric measurement solution with predefinable resolving power is evaluated.

2. The method according to claim 1, characterized in that the semiconductor radiation source are controlled during online production within idle times of a few milliseconds.

3. The method according to claim 1 or 2, characterized ge indicates that the light portion emitted from the linear or flat arranged semiconductor light sources is imaged on the specimen via collecting optics, and that the remitted light via a reduction optics as a sharp a visual image is projected onto the receiver surface, the CCD receiver elements being exposed and the amount of light supplied to them being integrated, as a result of which intensity patterns are generated which are compared in terms of their location and intensity with predetermined comparison intensity patterns.

4. The method according to any one of claims 1 to 3, characterized in that the projection scale between semi-conductor radiation sources and radiation projections onto the test specimen on the one hand and with respect to the remitted light between the light projected onto the test specimen and remitted by it onto the CCD Receiver on the other hand can be chosen arbitrarily.

5. The method according to any one of claims 1 to 4, characterized in that the activation times of the Semiconductor radiation sources of the individual spectral ranges are set in such a way that the amount of light received by the respective radiation normally reflected on a white is the same for all spectral ranges.

6. Apparatus for performing the method according to claim 1 to 5, characterized in that spaced semiconductor radiation sources (1) in the form of at least one row and / or columnar arrangement are connected to a control unit which the Halblei¬ Driven radiation sources so that they sequentially emit different spectral light (la to lc), which via a collection optics

(2) is projected as a line or areal image (3) onto the test object that a line or areal monochromatic CCD receiver with a large number of CCD receiver elements is provided, on which the

The specimen of remitted light is mapped in a geometrical assignment via a receiver optics (4) and that an evaluation device is connected to the CCD receiver, which evaluates the local patterns and / or the intensity patterns supplied by the CCD receiver for the different spectral ranges Evaluates intensity.

7. The device according to claim 6, characterized in that the evaluation device has stored predetermined intensity patterns and evaluates the currently measured intensity patterns taking into account the stored ones.

8. The device according to claim 6 or 7, characterized ge indicates that semiconductor radiation sources of different spectral ranges are arranged in a cyclically repeating periodicity to each other.

9. Apparatus according to claim 6 or 7, characterized in that the semiconductor radiation sources are arranged in a plurality of discrete rows or areas, each with the same spectral range.

10. Device according to one of claims 6 to 8, characterized in that at least two rows of semiconductor radiation sources are provided, wherein at least in one row semiconductor radiation sources with two different spectral ranges are arranged alternately.

ιι. Device according to one of claims 6 to 8, characterized in that semiconductor radiation sources are arranged in rows and columns in a surface and in a cyclically repeating permuting periodicity.

12. Device according to one of claims 6 to 8, characterized in that dichroic mirrors are provided for merging the radiation of the radiation sources.