DE3232577A1 - METHOD AND DEVICE FOR MEASURING COLOR CONCENTRATION IN PRINTED PRODUCTS - Google Patents

Description

1. Kotobuki Seihan Printing Co., Ltd., 4-26 Ueshio
6-Chome, Tennoji-Ku, Osaka, Japan

2. Dainippon Screen Mfg. Co., Ltd., 1-1 Tenjinkitamachi, Teranouchi-Agaru 4-Chome, Horikawa Dori, Kamikyo-Ku, Kyoto, Japan

Method and device for measuring color concentration in printed matter

The invention relates to a method for measuring
Ink concentrations in printed matter as well as a
Device for measuring ink concentrations in
Printed matter, in particular for the implementation of this process.

The invention is therefore a method and a device for measuring the dye or ink

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concentrations in printed matter, especially color printed matter, with measured concentrations processed and appropriately displayed so that the amounts of ink in a printing press are effective can be controlled and monitored. The invention also relates to the improvement of a measuring head, which can be used in a device for measuring ink concentrations.

It has been found to be more difficult to provide a numerical control system in a print shop than this in other departments, especially in development, correction or retouching Case is. For this reason, it has hitherto been necessary that the operators for printing machines in the Control of the printing process, in particular to maintain the high quality of the printed products produced, Make continuous use of your full experience and make full use of your six senses.

Each of the numerous duplicates should be printed exactly and evenly and in accordance with an individual Prototype or a single artwork (this is a printing standard that referred to as "OK sheet" and referred to below simply as "prototype"). So it should be everyone noticeable variation between duplicates can be avoided. For this purpose the operators the amount of ink and the amount of fountain solution used according to their experiences and sensations to be controlled manually.

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Recently, some methods have already been proposed which pursue the goal, quantitative to use working facilities instead of such empirical values. For example, in Japanese Laid-Open Specification No. 55-55232 describes a device which operates in such a way that colored spots are scanned by primary color inks on edge areas are supported, which surround the central area to be printed. The color concentrations of these Spots are measured in this way and compared with standard concentrations in each case. The ones in between Differences are visualized on a video display device (i.e. a television screen). The ink concentrations in printed products are therefore controlled on the basis of the displayed values Differences.

However, the device described above has some disadvantages. The color patches must namely on free edge spaces of printing papers are printed in a direction that is perpendicular to the printing direction, so that the necessary measurement of the concentrations of the. Primary color inks can be done. This entails a lengthy process time, since there are exact patterns for these spots on the cyan plate (C), the magenta plate (M), the yellow plate (Y) and the black plate (B) must to avoid any overlapping of the spots in the printing process with alternative use of the plates avoid.

It should also be noted that in the system described above, the printing papers have an excess width,

d. H. of about 7 mm, for the margins that remain free, on which the spots of color are outside the Main areas can be printed, as yes the main areas themselves necessarily through the image or the other figure to be printed must be filled in (in many cases it is difficult to to leave such additional areas free in printing papers). In addition, the color stains necessarily increase ink consumption, resulting in higher production costs.

Furthermore, is in the laid-open Japanese utility model application 55-148942 describes a device for measuring ink concentrations in printed products, which is constructed so that an ink adjustment screw can be operated remotely. The screw or auger is placed on an ink source of a printing press. In this way the device stabilizes the ink concentration, without the need to use the color patches described above.

However, this device also has a disadvantage and is for the same reason as one in the laid-open specification No. 55-55232 is not an ideal device. It is known that ink concentrations in some areas of the printed matter in the course of a continuous printing operation in offset printing or other printing systems. The change in the ink supply rate cannot can be detected directly, except in the case of a monochromatic print. It is in other words

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almost impossible to detect every such change exactly in every feed rate of multiple inks, d. H. that is, from C, M and Y inks if they are in Print products with different dot gradations are superimposed on one another (including 100%, i.e. so "massive"). It is difficult to solve this problem by simple means or measures such as Measurements using a red (R), green (G) and blue (B) 'filter, so trying to be reasonable Differences in the filtered densities between a sample of the printed matter and a printed standard in terms of feed rates for the C, M, and Y inks. Such difficulties rely on the indirect relationship between densities and feed rates and make it impossible to to control the rates successfully in order in this way to restore the changed densities to standard values bring back. Here, too, is the experience of trained operators, which has already been discussed necessary. In addition, it takes a considerably long time to accurately restore the color densities.

It has also already been proposed to use a proof press, so to produce proofs, their color densities as a standard for controlling the actual printing process in one Printing press can be used (sometimes referred to as a "base press"). The ink density differences between the However, both presses are often affected by a difference in the balance of the inks with the fountain solution Pressing or caused by a difference in compression pressing of the presses. Such an investigation therefore cannot effectively use the printed matter

stabilize quality, even if the color density deviations from the proof for each the R, G, and B filters are displayed or used as a measure to set the feed rates of C, M, and Y inks would.

In another document, Japanese Patent Laid-Open No. 55-55233, there is a reflective ink densitometer described, which enables scanning by means of a movable scanning head. In this scanning densitometer, the movable one is stationary Head not in contact with test points on printed matter. Accordingly, the head should be big be enough to adequately eliminate undesirable interference caused by light, which enters the space between the head and the printed matter. Such a large readhead but is unfavorable because namely its optical axis is difficult to align exactly with any given Checkpoint can be brought. This results in a lower accuracy and an inadequate Reliability in the quality control of printed products, the cause of intensified efforts and improvements are.

It should also be noted that in some cases where only an ink density measurement is made, an accurate one It is impossible to measure the quality of the print products because there is a double print, a blurring or similar. Such incorrectly printed portions have hitherto been used for analysis by means of a magnifying glass considered (for example with about tenfold

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Enlargement), whereby spots or halftone dots, which form the double or blurred printed image area, are optically enlarged. The areas that are caused by incorrect superimposition of cyan, magenta and yellow inks, however, are difficult to remove even by a skilled operator analyze, since the best experience can only be exploited if there is a really optimal magnification.

The invention is based on the object of providing a method and a device of the type mentioned at the beginning create that an accurate detection of variations in ink concentrations of printed matter, in particular Multicolor printed matter, in terms of cyan, magenta and yellow inks, allow so that the ink concentrations can practically be controlled with higher accuracy.

According to the invention, this object is achieved with a method of the type mentioned at the outset solved by a step in which the reflection densities of test points in one Printing standard together with reflection densities of test points in a sample of a printed product to be examined are measured, the last-mentioned test points corresponding to the first-mentioned test points in each case and thereby the same red, blue and green filters are used in both measurements; a Step in which the ink concentrations of inks that have been printed together on both printed products are calculated using color densities obtained using the three filters for each of the checkpoints to be measured; and a step in which, for each of the test points, the variations or their coefficients can be determined in the print product sample,

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where the variations are expressed as differences in ink concentrations defined between the printing standard and the sample of the printed product to be examined are.

Accordingly, a device according to the invention is characterized by a scanning head which is attached to each Any point above the printed matter can be moved and used for measuring color densities is set up by red, green and blue filters; a central computing and control unit for computing the variations or the coefficients of those variations in the ink concentrations in a printing standard and in a sample of the printed product to be examined, the measured color densities together with coefficients, which shows the relationships between each of the cyan, magenta and yellow inks and each of the color densities which means the red, green and blue filters are measured, represent, used; and a facility for displaying the variation or the coefficients thereof and / or a device for displaying Instructions relating to the control of ink feed rates in a printing press.

Thus, in accordance with the invention, any variation in the printed or transmitted amounts of the three Primary inks, i.e. C, M and Y inks, on the base the measured color densities are determined at suitable test points at which these three inks are used in multi-color printed products are superimposed on each other. Any impure component in the colors of the primary inks will

automatically excluded when determining the amount of ink transferred. Regarding this elimination process some explanations are given below.

Primary inks used in practice (abbreviated as C, M and Y inks) have colors which are different from the ideal ones Colors differ because, for example, the C ink too has impurities as small components that are exclusive to the other primary M or Y ink should be included. This also applies to the M and Y inks.

The reflection densities D _R , D and D, which at a pressure

Standard by means of a red, green or blue filter

can be roughly expressed by the following formula (1):

^D R ^{= r} 11 ^C 0 ^{+ r} 12 ^M 0 ^{+ r} 13 ^Y 0 ^D G ^{= r} 21 ^C 0 ^{+ r} 22 ^M o ^{+ r} 23 ^Y O ^D B ^{= r} 31 ^C O ^{+ r} 32 ^M O ^{+ r} 33 ^Y 0j '

where C_, M ₀ and Y_ are the printed quantities of C, M and Y inks at any printed point with overlay and IT ₁₁ , r ₁ ", ..., or r__ the ratios of color densities to these primary ink quantities express, with measurement of the densities through the filters of the three primary colors.

Similarly, the reflection densities become a Sample of an actual printed product

represented by the following formulas "(2):

V ^{= r} 11 ^C 1 ^{+ r} i2 ^M 1 ^{+ r} 13 ^Y i "

^D G ^{f = r} 21 ^C 1 ^{+ r} 22 ^M 1 ^{+ r} 23 ^Y 1 ^D b ' ^{= r} 31 ^C 1 ^{+ r} 32 ^M 1 ^{+ r} 33 ^Y yJ

This density measurement is carried out using the same filters as those used for the pressure standard, and is carried out so that the measured test points correspond to those of the printing standard.

In the device used according to the invention, as well as in the method proposed according to the invention, the above simultaneous equations (1) and (2) are processed in such a way that the values C-, M, Y_, C ₁ , M and Y .. are obtained therefrom . Then the differences

= C ₁ - C _Q , / IM = M ₁ - M _Q and 4Y = Y - Y _{Q are} calculated and used to adjust the feed rates of the C ink, the M ink and the Y ink. It is obvious that any disturbing influence which could be caused by the impurities present in the C, M and Y inks can be excluded by the method steps described above.

The device provided according to the invention has, as claimed, a scanning head, a central one Computing and control unit and a display device. The readhead can be at any point desired of a printed matter on which color densities are measured by means of filters which the head has should be moved.

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The central control unit is programmed to make the calculations necessary to determine the printed amounts of cyan, magenta and yellow inks based on the color densities that are performed by the red, green and blue filters are measured. This control unit then compares these amounts of ink . in the print standard with those in samples of commercially produced print products and calculates the Differences as such or their relationships to the standard values.

The display means described above is arranged to display the thus calculated Differences or their relationships or the necessary control measures indicates which are required to determine the ink feed rates of a printing machine based on these differences or To adjust relationships.

In a preferred embodiment of the invention, the scanning head has a magnification device which is arranged on it at a certain distance from the density measuring device and which can be moved relative to the printed products. The magnification device allows easier observation of the test points, so that they alternate in correct. ■ ' Alignment with the optical axis of the measuring part can be brought.

Further features and advantages of the invention emerge from the claims and from the following description, are explained in detail in the exemplary embodiments with reference to the drawing. It shows:

Fig. 1A is a graph showing the relationship between color density and incremental feed for each of the primary inks;

Fig. 1B shows another relationship between the color density and increasing Compression molding;

Fig. 2 shows an output on a cathode ray tube or on a line printer;

3 shows a perspective illustration of an embodiment of the device according to the invention with a color test stand for measuring ink concentrations in Artwork;

Figure 4 is a block diagram of the apparatus of Figure 3;

5 shows in a flow diagram the sequence of the steps according to the invention Procedure steps carried out;

6 shows an exemplary embodiment of a sensor head in a front view portable reflection color densitometer; and

7 shows the sensor head from FIG. 6 in a top view.

Example I.

An embodiment of the method of the present invention for measuring ink concentrations is shown below with reference to Figures 1 A and 1 B explained.

In the invention, several significant sections of an original (or an image) are used instead of the known Color stains that have been marked using the state-of-the-art in multi-color printing, selected as checkpoints. At these checkpoints are generally three colors or inks superimposed on each other, the color densities of these colors being measured to to be able to analyze any change in the printed concentrations of these inks using the measured data.

These three types of inks are usually cyan (C), magenta (M), and yellow (Y), so that's theory or the principle of the aforementioned analysis will be explained with reference to these inks. As in the prior art is known, the actual C, M and Y inks have colors that differ more or less from the ideal colors. For example, the C ink has a pure basic

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component to unite with impure components on the should only be contained in the M or Y ink per se. Such impure compositions exist similarly in the M and Y inks. Table 1 shows an example of the impurities, where the numbers indicate color densities, which with a red filter (R), a green filter (G) and a blue filter (B) have been measured with each of the C, M and Y inks independent with a dot area ratio of 100% (i.e. the inks are printed over the entire sheet have been printed on a suitable sheet of paper.

Table 1: Color densities of C, M and Y inks, measured with R, G and B filters, respectively

by R filter C ink , 79 M ink , 25 Y ink , 08 density by G filter 1 , 55 0 , 85 0 , 17th density by B filter 0 , 22 1 , 04 0 , 05 density 0 1 1

Table 2 shows the proportions of the pure and impure components, which have been converted into decimal fractions, by taking each the "predominant density" through a filter with the complementary color of each ink in table 1 was used and set as 1.00 (for example, the "predominant density" is the density through the R-filter in the case of C ink, because red is the complementary color of this ink, so this predominant density is below referred to as "C component" for the C ink),

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Table 2: Ratio of the impure components of the C, M and Y inks

relationship C ink , 000 M. -Ink Y ink _r O76 C components relationship 1 , 307 O , 135 0 , 162 M components relationship O , 123 1 , 000 0 , 000 Y components O O , 562 T

The densities through the R, G and B filters, ie D _n , D_ and D_, are approximately represented for a standard printed product by the following formulas for each point at which the aforementioned inks are printed out superimposed on one another Point area ratios differ from one another (or the ratios can be the same):

where the variants C _Q , M _Q and Y _{Q are} the superimposed printed amounts of each ink (C, M and Y-Tine) at the test points and the coefficients or factors r ₁ .., r ₁₂ , ..., r _{33 are} the ratios mean each density through the filters of different color to the corresponding prevailing densities.

^D R ^{= r} 11 ^c o < ⁰ G = ^r 21 ^c o ^{H 0} B = ^r 31 ^c o ^H ' ^r 12 ^M 0 " ^{V r} 22 ^M o ^{H hr} 32 ^M O ^{H V r} 13 ^Y 0 ^hr 23 ^Y O ^hr 33 ^Y O

In the example shown in Table 1 above, the C ink has its pure and impure components

talking factors

= 1.000, r ₂₁ = 0.3O7 and r ₃₁ = 0.123,

while the M ink has factors r ₁₂ = 0.135, r ₂₂ = 1.000 and r ₃₂ = 0.562. The Y ink, on the other hand, has factors

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r ₁₃ = 0.076, r ₂₃ = 0.162 and T ₃₃ = 1.000.

Assuming that the color densities measured on a regularly printed curve are D _R ', D' and Dg'r using the R, G and B filters to detect portions corresponding to those in the standard printed matter, so let the densities

Express D ', D' and D 'in a similar way as follows: RG B

⁰ R ^{1 = r} 11 ^C 1 ^{+ r} 12 ^M 1 ⁺

D '= r C + r M + r Y C_ ... (2)

^D b ' ^{= r} 31 ^C 1 ^{+ r} 32 ^M 1 ⁺

where the variants C., M ₁ and Y denote the respective amounts of ink printed out overlay.

The above color densities can be subtracted from the densities discussed first by each of the filters R, G and B for the standard printed matter, respectively. The differences resulting from these calculations, ie " ^D R ^{= D} r '- V ⁴⁰ G ⁼ V - ^D G ^and " ⁰ B = V - V , however, have no practical significance, since all these values are in an irregular manner due to the impure components in the inks are affected and enlarged. If these differential values were simply used to control the ink feed rates, they would be overly altered.

In contrast, the method according to the invention uses direct differences resulting from the printed concentrations of C, M and Y inks, respectively, measured in both

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Printed products. These direct indices are ^ c = CL - C, 4M = M ₁ -M and AY = Y - Y, whereby any error caused by the ink contamination mentioned is eliminated from these differences, so that the ink feed rates are now precisely controlled can be.

_Q ,

The aforementioned ink concentrations C, M_ and Y are calculated based on the equations (1), while C, M ₁ and Y are similarly obtained from the equation (2). Accordingly, the respective ink concentration differences de, ΔΜ and / JY can be calculated as follows:

⁴⁰ R ^r 12 ^r i3

^r 22 ^r 23 ^r 32 ^r 33

.4M =

^r 11 ^{A] r} 21 ^{Λ r} 31 ^{Λ1 D} R ^r 13 ³ G ^r 23 ³ B ^r 33

^r 11 ^r 12 ^JD R ^r 21 ^r 22 ^ ^O _G ^r 31 ^r 32 ^ΔΌ _Β

BOEHMÄRT ÄBÖEJJMERT \

where R =

11th
^r 21

^r 12 ^r i3 ^r 22 ^r 23

^r 31 ^r 32 ^r 33

is substituted for the above denominators.

If desired, the deviation ratios can also be determined from the following equations (4):

= C x 100

■ 4M
£ M = M x 100

ΔΥ £ Y = Y ₀ x 100

Equations (1) and (2) above are apparently not completely correct because there is an irregularity in the addition of algrebraic terms (i.e. r ^ C, r ^ ₂ ^M _O etc.), in addition to irregularities in the proportions between the variates ( ie C_, M etc.) and the algebraic functions (ie D_, D etc.). It is

K G should be noted, however, that in the process according to the invention minor changes in ink concentrations are just the problem, so that such irregularities do not affect the validity of equation (3).

When applying equation (3) it is necessary to

first the factors

to investigate.

. ₁ , r .. ,,, ..., T ₃₃ These factors can be obtained by measuring color densities using the R, G and B filters for each available ink, each of these inks individually having a dot area ratio of 100% printed on paper. Some of these factors, which are sufficiently small, can be neglected or treated as "zero"

will.

To be precise, the aforementioned factors vary slightly dependent on scales (i.e. the point area ratios vary from 0% to 100%) for each of the C, M, and Y inks. The factors for a point area ratio of about 50% are closer on the mean values so that these instead of those for a point area ratio, if desired of 100% can be used. Several factors can be considered if greater accuracy is desired for each test point according to its respective point area ratio be used. To do this, a number of factors are used for each ink and each Filter intensively in advance over the entire range of point area ratios in regular steps investigated (thus working out the above equations (1)). Such accuracy is normally not required in practice, however, since the method according to the invention is only used for control small deviations in the ink concentrations is applied.

The method can be easily applied even in the occasional case where a black ink (BK) is added is added to the three primary inks already discussed (i.e., C, M, and Y inks). That discussed Namely, the calculation scheme does not require any modification if the variation in the BK ink concentration is negligible is. If there is likely to be greater variation in this, it becomes appropriate Device used to analyze the concentration of BK ink and its variation at test points where

this ink is printed out so that any influence of this ink is subtracted from the other basic data can be.

On the other hand, if one of the C, M, or Y inks is absent, a color filter should be used for the "Dominant density" of the absent ink is omitted from the measurements discussed above will. The simultaneous equations (1) and (2) change accordingly into a system of dual equations. Also the resulting equations (3) are modified and solved in a corresponding manner. If some points in If the printed image has only one ink, such test points will of course only be made with a single one Filters measured for that ink to determine the corresponding prevailing density.

In the event that one or more special inks have colors different from those of the C, M and Y inks are different, their concentrations would be simplified using equations (3) or more Shapes of the same checked, insofar as they are printed points at which two or three such specialty inks are superimposed on each other. At the other print points where only such special ink is printed out, it is sufficient Use R, G, B or W (white) filters to track the color density change in these monochromatic Points to consider.

Various methods of further processing and / or using those obtained by the above method

Data on ink concentration differences are explained below along with an example of how this difference is displayed.

Working method 1

Fig. 1 A shows a variance in the measured ink concentrations, the solid line corresponding to a standard ink feed rate, while the dotted Lines correspond to increased or decreased ink feed rates in a printing press. The point area ratio is taken as another variant on the horizontal axis. The graphic Graph shows that the coefficients of variance from the standard are nearly equal to each other regardless the positions of the test points, d. H. Highlight (H), Central (M) or shadow (S) areas of a print template.

The above coefficients of variation are according to calculated from equations (4) in the following way:

/ c _H - loo χ (c _H1 - c _H0 ) / C ₁₁₀ (%)

<fC = 100 x (C _Λ - C.) / C 0 (%) and m mi mo m

<rc _s = loo χ (c _sl - C ₃₀ ) / c _so (%) ... (5).

These equations are an example of the case of the cyan (C) ink, and give a result in which the values fC _R , SQ ^ and ^ c _g are almost equal to each other.

Will appear on a display device or an alarm device a warning signal, which the operator to readjust

the ink supply rate when the coefficient of variation has a predetermined upper or lower limit have exceeded. This applies equally to the magenta (M) and yellow (Y) inks.

Working method 2

Fig. 1B shows a variance in the measured ink concentrations as a function of both a change in the printing pressure and a change in the dot area ratio, the solid line representing a standard pressure or a standard pressure, while the dotted lines represent a changed pressure in a running printing press . The point area ratio is also used here as another variant. As is to be expected, a warning signal appears in a similar manner on a display device and / or an alarm device if, for example, the coefficient of variation <fC _{TT of} the C ink concentration

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has become extremely larger in the highlight portion (h) than in the central portion (m) and has exceeded a limit value Has. The compression is then adjusted accordingly.

Working method 3

In multi-color printing, it is sometimes observed that a post-printed ink (the second ink) does not work properly can be transferred to a preprinted ink (the first ink) which is not yet sufficient has dried (this phenomenon will be referred to as "poor adhesion" below). Generally rise

the coefficients of variation of the ink concentrations in the shadow portion (s) in which the point area ratio is close 100% is more extreme than in the middle section or in the middle sections (m). If this coefficient has exceeded a limit, the "bad stick" will similarly appear on a display and / or alarm device displayed.

Working method 4

In the event that an extreme change in the coefficient of variation of the ink concentration is none of the above the circumstances discussed could be the possible reason for such a change in general be a bad balance between the ink and the fountain solution. A warning sign which gives an order to readjust this balance, then appears on a display and / or alarm device.

Whenever you work, it is better to have a color filter to measure the brightness of each test point at the same time to use and thereby a difference in the color density of the printed product compared to a standard to display. Such data is also recorded on a cathode ray tube or on a printer along with the above The coefficients of variation of the C, M and Y ink concentrations discussed are shown so that the latter can easily be checked by the human eye. Fig. 2 is an example of the obtained Output graphs on a cathode ray tube or on a printer, the graph showing that the

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Magenta ink concentration has risen abnormally high is and the upper limit at a checkpoint that starts with "1" is designated has exceeded.

Example II

An embodiment of a device according to the invention, by means of which the above-described Process can be carried out will now be explained with reference to FIGS.

As shown in FIG. 3, the apparatus has on a base part 100 an inclined table 102 which holds a printing paper 106 can accommodate. Rails 103 are attached to the right and left ends of the table, respectively. A frame 104 movably connected to the rails 103 has a scanning head 105 connected to the frame and is movable from side to side to the right and left. In this way, the scanning head 105 brought to any desired position in opposition to any test point on the printing paper by moving it in the direction 107 indicated by an arrow.

At the front of the base part 100 there is a control panel 108 and cathode ray tubes 109, "109 ', which are easily are operable. The control panel and cathode ray tubes are suitable for processing and visualization measured data.

At the rear of the base part 100 is an upright one

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Plate 111 is provided, which is a printing standard 110, who is glued to it, carries. Standard light sources 113 are attached to a cover part 112 Cover part 112 is arranged above the upright plate 111. The light sources produce rays of light emitted downward through a honeycomb structure of a cover 114 below the cover part. curtains 115 hang from the right and left ends of the Roof 112 so that they can move in the direction of arrows 116, which prevents that unnecessary light rays get into the interior.

In the following, with reference to Figures 4 and 5, details of the device described above explained in terms of their structure and mode of operation.

1st stage: return to the starting point

First, a voltage source is switched on by means of a switch (not expressly shown) on the control panel 108 (Step 50 in Fig. 5) so as to provide pulse motors 31 and 32 respectively by means of motor drive circuits 33 and 34, which in turn are activated by a central control unit 22 via a connection 28. the Control unit 22 is provided with a program which ensures the voltage supply to the circuits 33, 34. The motors 31, 32 enable the drive of the scanning head 105 and the frame 104 until they reach their Starting points have arrived. The scanning head 105 is along the frame 104 in the X direction by means of a

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corresponding device, such as a worm drive, which is operatively connected to one of the aforementioned motors, moved to the right and left. The frame 104 itself is moved along the rails 103 in a Y-direction by another motor. Position sensors 35, 36 are also connected to the connection 28, which sense a starting point marking, whereby the two motors are stopped and the drive head is _{held stationary at the starting point (X 0} / Y _n ) (step 51 in FIG. 5).

2nd stage: Presetting of the test points

The printing standard is then placed on the inclined table 102 and at one end with a suitable one Display device (not shown) brought into correct alignment, so that the printing standard 110 arranged at a predeterminable correct position on the table 102 and there by known suction devices can be set.

Thereupon provided on the control desk 108 switches for manual control of the scanning head 105 by means of the motors 31, 32 already discussed are operated. The scan head 105 thus becomes the first test point moved and temporarily held there (step 52 in Fig. 5). Then button switches will be on the control panel 108 to input position information into the cathode ray tube unit (step 53 in Fig. 5), this operation being repeated until all of the position data for the other checkpoints have also been input to the cathode ray tube unit.

3rd stage: Measurement on the pressure standard

After the preset has been completed, the measurement of the color densities of the printing standard started by pressing other button switches (not specifically shown) on control panel 108.

The scanning head 105 is automatically driven in accordance with a previously stored program (step 54 in Fig. 5). All other checkpoints are sequential measured, each measurement with the R, G, B and W filters takes place so that the color densities D_, D ^, D_ and D_ "received into the cathode ray tube unit T09 are to be entered via a connection 23 (step 55 in FIG. 5).

The cathode ray tube unit then calculates the ink concentrations from the above data Co, Mo and Yo (step 56 in Fig. 5), before this data processing are the factors corresponding to the pure and impure components (i.e., therefore, r 11, r etc.), each ink already given to a "semi-solid" data device 27 and the cathode ray tube unit 109 via a connection 26 and a bus line (the aforementioned factors depend on the types of ink used).

Obviously, the color density data, on the contrary, also of the cathode ray tube unit simultaneously can be supplied with the position data of the test points.

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4th stage: Regular measurement

After the previous measurement on the pressure standard, a regular measurement is then started. To this The purpose is a printed paper (for sample) from a number of printed papers or printed products selected, which are continuously discharged by a printing press. The sample is on the inclined table 102 arranged and determined, as has already been described, whereupon a start push button (not expressly shown) is pressed on the control panel 108 to automatically set the drive head 105 to the test points to let the other pass (step 57 in Fig. 5).

In this way, the color densities become D ', D ¹ , D' and D ¹

RGB

measured by the scanning head (step 58 in Figure 5). Subsequently, the cathode ray tube unit 109 calculates the ink concentrations C ₁ , M and Y ^ (step 59 in Fig. 5), which in turn have been obtained with the already obtained concentrations Co, Mo and Yo for the standard point, from which the coefficients of variation are obtained (as shown by the above equations (4) discussed). These are then checked to determine whether or not they fall within permissible ranges that can be specified (step 60 in FIG. 5) 22 via connections 24 and 25, respectively, are displayed (step 63 of FIG. 5). A template for such a graphical representation is shown in FIG.

If the check results in a "no", then there is Warning signal on an alarm device 30, for example a warning lamp, an alarm bell or the like, which with the control unit through a connection 29 (step

61 in Fig. 5), so that the operator immediately comments that there is an abnormal operating condition in the printing process.

In addition, any of the following applicable instructions or information will appear on the cathode ray tube 109 or another display device (step

62 in Fig. 5) reproduced:

(a) "Ink supply rate should be adjusted"

(b) "Compression pressure should be adjusted"

(c) "There appears to be poor adhesion"; and

(d) "The balance of the ink with water should be improved will".

A check that all test points have been measured are or not, then takes place (step 64 in FIG. 5) If the answer is "yes", the routine ends here. However, if the answer is "no", the method described above is started again with step 57 (step 65 in Fig. 5). After completion of this run, the operator sets the printing press according to the Instructions.

This fourth step, as shown in FIG. 5, is used for each further sample sample taken of the printed matter repeated during the printing process, so that

good conditions in the ink concentrations can be easily and reliably maintained.

The methods and steps described above can of course also be applied to the variations as such, rather than their coefficients.

The device according to the invention has numerous advantages in that it can correctly detect changes in ink concentration for each test point, where it does not suffer from the irregular relationship between ink concentration and color density. The device is also advantageous in that it provides both a warning signal and an operating command based on the Analysis of deviations provides so that even an inexperienced operator can operate the press easily and quickly can readjust, whereby material losses are reduced. When the device is in a known color test stand is built in, a visual inspection makes control more effective. A control circuit can can be combined with the device in such a way that the analysis data supplied by the device are fed to the circuit, whereby the printing press is then controlled or checked fully automatically can be.

Example III

Another embodiment will now be described in which a color density measuring head, i. H. a Scanning head, which is better for a combination with the device described in Example II

BOEHlViEJiT; & BOEHMERP ". ^: .: λ 32 32577

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is suitable and which is shown in Figures 6 and 7.

A head holder 201, which is movable in the X direction and supported by a frame 205 which is movable in the Y direction, has a density detector 202, a lighting device in the form of a point radiator 203, which enables easier confirmation of the test point positions, and a television camera 204, which is provided with a microscope lens (with a magnification of approx. 150). All of these components are attached to the head holder with a spacing of L ¹ and L between two components. A magnifying projector can also be used in place of the television camera 204. Here, too, the reference numeral 102 denotes a printing paper. The camera or projector is described below as the "enlarger".

In operation, the point source 203 is switched on, whereupon it emits a light beam, which the test point that is supposed to be discriminated against by the background that surrounds it. When a density measurement is carried out, the head holder 201 is moved by the distance L 'between the point radiator 203 and the Density detector 202 shifted so that the test point is in alignment with the optical axis of the detector comes.

To observe the shape of a spot within the test point, the head is similarly around the Distance L between the detector 202 and the television camera 204 shifted, whereby the test point in the ent-

323257?

Speaking way is brought into alignment with the optical axis of the microscope lens, which with connected to the camera. An image signal from the television camera having the microscope lens, is put on a cathode ray tube monitor (advantageously a multicolored one), so that so there an enlarged image of the spot appears. The projection is preferably about 150 times Magnification so that several people can observe the stain at the same time.

In. In the event that several test points are selected from the printing paper 106, the point source 203 should be brought to the selected points one after the other and correctly focused on them so that all XY coordinate values can be supplied to a memory and stored there. The distance L ¹ is then subtracted from (or added to) the stored values so that the correct positions can be determined. The detector 202 can in this way be set to the correct positions of the test points during the movement of the scanning head. The color densities of the numerous test points are automatically measured with high precision and also very quickly and efficiently when operated in this manner.

It is of course possible to carry out a density measurement for each test point following the focusing of the point source 203, the subtraction or addition of the distance L ¹ between the two steps then taking place.

The structure of the scanning head described above

- "SS -

can be used not only in the manner described in reflection densitometers, but also in Transmission densitometers. Instead of the point source, a viewing device with low magnification, almost natural size, which in the other case is adjacent to the Microscope lens of the television camera can be provided.

The structure described above ensures correct alignment of the test points with the optical Axis of the detector in a movable density measuring head. The enlarger, i.e. H. so the television camera, has a microscope line that replaces the well-known magnifying glass and an extremely enlarged one Image of a fine spot so that even inexperienced operators can observe at the same time and can analyze any discrepancy or blurring in it easily and precisely. This lets monitor print quality more effectively.

File: KX 1050

BSZUG3ZSI0HENLI.3T2 (LIGT OF RSPSRENOiS

1 Alarm device 1 2 2 3 Control unit 4th link 4th 5 link 5 6th link 6th 7th link 7th 8th Data setup 8th 9 link 9 10 link 10 11th 11th 12th 12th 13th 13th 14th 14th 15th 15th 16 16 17th 17th 18th 18th 19th 19th 20th 20th 21 21 22nd 22nd 23 25th 24 24 25th 25th ? fi P6 27 21 28 28 29 29 30th 30th

engine 31 32 engine 32 33 Drive circuit 33 34 34 35 Position sensor 35 36 Position sensor 36 37 37 58 38 39 39 40 40 41 41 42 42 43 43 44 44 45 45 46 46 47 47 48 48 49 49 50 step 50 51 step 51 52 step 52 53 step 53 54 step 54 55 step 55 56 step 56 57 step 57 58 step 58 59 step 59 60 step 60 61 step 61 62 step 62 63 step 63 64 step 64 65 step 65

d6 Base part 66 67 67 68 68 69 69 70 70 71 71 72 7? 73 7 ⁷ > 74 ψ \ 75 75 76 76 77 77 78 78 79 79 80 80 81 81 82 82 S3 83 84 84 85 85 86 86 87 87 88 88 89 89 90 90 91 91 92 92 93 93 94 94 95 95 96 96 97 97 98 98 99 99 100 100

101 101 - ^ 02 table 102 10J rail 105 104 · frame 104 105 readhead 105 106 printing paper 106 107 direction 107 108 control panel 108 109, ¹⁰⁹ 'cathode ray tube 109 / 110 printing standard 110 111 plate 111 112 cover part 112 113 standard light source 113 114 cover 114 115 curtain 115 116 arrow 116 117 117 118 118 119 119 120 120 121 121 122 122 123 123 124 124 125 125 126 126 127 127 128 128 129 129 130 150 131 131 132 132 135 155 134 154 155 155

201 Head holder 201 202 Density detector 202 203 Point source 203 204 Television camera 204 205 frame 205

_ C _M

. WF-.

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Claims (12)

KX 1050 Expectations / 1. Procedure for measuring ink concentrations in ! Printed products, characterized by a step in which the reflection densities of test points in one Printing standard together with reflection densities of test points in a sample of a printed product to be examined are measured, the last-mentioned test points corresponding to the first-mentioned test points in each case and thereby the same red, blue and green filters are used in both measurements; a Step in which the ink concentrations of inks that have been printed together on both printed products are calculated using color densities obtained using the three filters for each of the checkpoints to be measured; and a step in which, for each of the test points, the variations or their coefficients in the printed product sample, with the variations being expressed as differences in ink concentrations defined between the printing standard and the sample of the printed product to be examined are. 2. The method according to claim 1, characterized in that that the calculation of the ink concentrations is done using the following equations: ⁰ R = ^r 11 Co + ^r 12th + ^r 13th Yo; ⁰ G = ^r 21 Co ⁺ r 22 ^MO + r 23 Yo; ⁰ B = ^r 31 Co + r 32 ^MO + r 33 Yo, where the values Co, Mo and Yo are the ink concentration of cyan, magenta and yellow inks, which are arranged on top of one another during printing, the values D, D "and D _D color densities, which are determined by means of a red, green or yellow ink .Blue filter are obtained, the values r ^, r ₁₂ and r ₁₃ coefficients, which correspond to the cyan, magenta and yellow components of the cyan ink, the values ^ ₂ -, r ₂₂ and r ₂₃ coefficients, which correspond to the cyan , Magenta and yellow components of the magenta ink, and the values of L., r ₃₂ and r ₃₃ , respectively, represent coefficients corresponding to the cyan, magenta and yellow components of the yellow ink, respectively. 3. Device for measuring ink concentrations in printed products, characterized by a scanning head (105), which can be moved to any point above the printed matter and is used for measuring color densities below Use of red, green and blue filters is established; a central computing and control unit (22) for Calculate the variations or the coefficients of these Variations in the ink concentrations in a print standard and in a sample of the print product to be examined, taking the measured color densities along with coefficients showing the relationships between each BOEHMBBT & JBOÖHfasstff ' -.r .'S. 3 2,325 the cyan, magenta and yellow inks and each of the color densities determined by the red, green and blue filters, respectively to be measured, represented, used; and means (109, 109 ') for displaying the variation or the coefficients thereof and / or a means for reproducing commands with regard to the control of ink feed rates in a printing press. 4. Apparatus according to claim 3, characterized in that the central control unit (22) for generating a Command that the ink supply rates should be adjusted when the variations or their Coefficients in the ink concentrations for highlight, middle, and shadow portions are close to each other equal to and outside of permitted, specifiable areas for the sample of the printed product to be examined are set up. 5. Apparatus according to claim 3 or 4, characterized in that the central control unit (22) for generating of an instruction that a printing pressure should be set when the variation or its Coefficient in the ink concentrations for the highlight portion is greater than that for the central portion and outside a permitted, predeterminable range for the sample of the printed product to be examined is, is, is set up. 6. Device according to one of claims 3 to 5, characterized in that the central control unit BOEHMBRTP & Ή0ΕΗΜΕΚΓ:: .- "ο ο ο ο C 7 OZOZO / / (22) is set up to indicate poor adhesion in the event that the variation or its Coefficient in the ink concentrations for a shadow portion greater than that for a central portion and outside of a presettable setting that is permitted for the sample of the printed product to be examined Area. 7. Device according to one of claims 3 to 6, characterized in that the central control unit for generating a command, according to which the ratio should be set between the inks and the fountain solution in the event that the Variations or their coefficients in the ink concentrations for the highlight, middle and shadow sections different from each other and the variations or their coefficients for the highlight and the Shadow section are so much smaller than for the central section that they are more allowable, more presettable outside Areas for the sample of the printed product to be examined lie. 8. Device according to one of claims 3 to 7, characterized by an associated color test stand. 9. Device according to one of claims 3 to 8, characterized in that the scanning head (105) has a Density detector (202) and a magnification device (204), which are arranged at a distance and relative are movable to the printed matter. 10. The device according to claim 9, characterized in that that the enlarger is a television camera (204) with attached microscope lens and a cathode ray tube unit cooperating with the camera. 11. Apparatus according to claim 9 or 10, characterized in that the scanning head (1O5) has a lighting device (203) which is at a distance from the density detector (202) and the enlarging device (204) is arranged and adapted to bring the scanning head (105) into alignment with the test point. 12. Apparatus according to claim 9 or 10, characterized in that the scanning head (105) has a lighting device (203) which is at a distance from the density detector (202) and the enlarging device (204) is arranged and set up to use a point beam when aligning the scanning head with the test point to create.