JP2906804B2 - Halftone area ratio determination device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to Y (yellow), M (magenta), C (cyan) and Bk (black) plates for printing based on density values measured on an object such as a color sample. In particular, the present invention relates to a device for determining a dot area ratio of a printing plate, and particularly determines a dot area ratio of each plate in the case of a combination of two colors out of three colors of Y, M and C and Bk. It concerns the device.

[0002]

2. Description of the Related Art Heretofore, there have been cases where a number of color samples have been attached to a printing layout paper for color designation. For example, when it is desired to uniformly fill the background with a specific color, a small piece of paper having the background color is attached as a color sample.

[0003] When printing a designated portion in the same color as the color sample, to determine what halftone dot area ratio each of the Y, M, C and Bk plates should be printed, a 10% interval is used. The color chart printed with the halftone dot area ratio changed to a degree and the color sample are compared sensuously by a person, and those that are sensually determined to be most similar are selected. In general, the percentage of the halftone dot area ratio of the plate is determined using the fact that it is described in the color chart.

However, in this method, not only the time is required for comparison, but also the color selected from the color chart is often different depending on the operator, and the determined halftone dot area ratio is likely to differ between the operators. There were drawbacks. At this time, the only countermeasure for determining the dot area ratio faster and more accurately was at most the level expected of a person skilled in this work.

[0005] However, even the above measures are extremely incomplete in terms of stably obtaining quick and accurate decisions, and it is still not enough to contribute to a production site that requires high productivity. It was a situation that had to be said to be enough.

On the other hand, a reflection densitometer is currently on the market that can measure the density of an object to be measured and calculate the dot area ratio. In the densitometer, the measured density value is processed by a microcomputer built in the densitometer to calculate a dot area ratio. The Yule-Nielsen equation is usually used to calculate the dot area ratio from this density value.

In order to use this Yule-Nielsen equation, a reference density is measured in advance, and the dot area ratio of the portion is set to a reference value (100%). It is necessary to measure the object to be measured for which the area ratio is to be obtained, and use the relationship with the reference concentration.

Therefore, it is applied only to a color having a reference density, and is usually used only for a single color.

In addition, the Yule-Nielsen equation reproduces an ideal halftone dot without a dot gain, etc.
In addition, since it is established by appropriately setting the coefficients that vary depending on the screen ruling, density, and transparency of the paper, a wide range of halftone dots from the light part to the shadow part can be used in actual use, even if they are monochromatic. The area ratio cannot be obtained accurately. Even more, the calculation of the dot area ratio for secondary colors or more
It's quite difficult, and it's not very satisfactory for practical use.

Therefore, such a densitometer cannot display the dot area ratio for expressing the color of the color sample for each of the Y, M, C and Bk versions in combination.

Further, such a densitometer has a dot area ratio of Y and Y for expressing the color of the color sample for the following reason.
M, C, and Bk cannot be displayed in combination for each version. That is, the Y, M, and C inks of the printing ink are not ideal. The Y ink contains the M component and the C component, the M ink contains the Y component and the component, This is because the ink contains the M component and the Y component.

More specifically, Y, M,
Since the printing ink of C is not ideal, the color of the object to be measured such as a color sample is changed to B (blue violet), G (green), and R (red), which are complementary colors of Y, M, and C. The density value obtained by measuring through each filter is
Even if the dot area ratio is calculated using Nielsen's formula, the value does not indicate the actually required dot area ratio of each of the positives Y, M, and C.

This will be more clearly understood by the following example. For example, it is easy to understand if it is assumed that an image having a dot area ratio of 100% is printed using only a printing ink of C of a certain ink maker.

That is, the printing material is defined as an R filter and a G filter, respectively.
When the density is obtained through a filter and a B filter, they are 1.53, 0.52, and 0.17, respectively. As is well known, the above-mentioned values are respectively set to the complementary colors of B, G, and R. It is a well-known content that it cannot be used to determine the dot area ratio of each of the Y, M, and C plates.

Further, such a situation becomes more and more complicated when not only one color ink but also a plurality of colors of ink are to be overprinted.

By the way, normal printing is Y, M, C, Bk
Are printed in four colors by each of the four color plates consisting of the following three colors. In contrast, the color of each part is a total of three colors consisting of any two of the three colors Y, M, and C and Bk. There are printing or plate making techniques that are configured. So-called achromatic printing and achromatic decomposition (printing method,
ICR decomposition, also known as decomposition method or plate making technique,
GCR decomposition or polychromatic plate making).

The function of the achromatic decomposition and the like is that the so-called UCR process is performed until one of the three colors of Y, M, and C is completely eliminated, so that the gray component resulting from the multiplication of the three colors is completely Bk. Is achieved by substituting

Here, suppose that Y is 90%, M is 50%, C
When a portion having a color of 20% is considered, the portion where the amount of ink is the minimum is 20% of C, so that 20% of the multiplication of the three colors of Y, M, and C can be said to be a gray component. In other words, at this time, by applying the UCR processing amount at 100%,
20% of the Y, M, C components can be replaced to Bk.

In the conventional UCR processing, undercolor removal is performed from the middle to the shadow part. However, in achromatic decomposition, etc., not only a large amount of UCR processing but also undercolor removal from the highlight part to the whole area is performed. Done. still,
In actual printing, it is often observed that the UCR process is not usually performed up to 100%, but is performed at approximately 50 to 60%.

According to achromatic decomposition, etc.,
(E) Since the total amount of ink can be greatly reduced even in the shadow portion where the amount of ink is maximum, the printability in high-speed wet printing is greatly improved. (F) Conventionally, the tertiary color portion is Y, M , C, but the color tone changes very little because Bk is the basis according to achromatic decomposition and the like, and (g) the inks of Y, M, C
Since the ink is replaced with k, the amount of expensive Y, M, and C color inks used is reduced, and advantages such as a significant reduction in the cost of the ink can be obtained.

However, when achromatic separation is performed, the state of the plate surface of the separation plate is completely different from that in the case where the separation plate is composed of four ordinary colors. Therefore, even with the above-mentioned skilled person who has also been involved in the printing method of four colors, the processing operation relying on humans can quickly, accurately and stably optimize the halftone dot area ratio of each of the three colors. It was a difficult task to decide.

[0022]

DISCLOSURE OF THE INVENTION The present invention has been made in view of the above-mentioned problems, and has as its object to make it difficult for even an expert to make quick, accurate, and stable judgments. In addition, the work of determining the optimal halftone dot area ratio in which the variation in the judgment among the workers occurs, that is, for any color, the color is set to Y,
When printing with inks of each color of M, C, and Bk, the gray component obtained by multiplying Y, M, and C is replaced with Bk, and any two of the three colors of Y, M, and C and Bk are used. When printing with a total of three colors of ink, the task of deciding how to combine the optimal halftone dot ratios of the plates of each color is difficult, even for beginners with little experience. It is an object of the present invention to provide a halftone dot area ratio determining device which can easily process the image data even when making a judgment.

[0023]

Means provided by the present invention as means for solving the above-mentioned problems are as follows.

A dot area ratio determining device described below, ie,

(A) Color density-dot area ratio conversion indicating a correspondence between a combination of color densities and a combination of halftone dot areas corresponding to the combination of color densities of a plurality of color separations. First storage means in which a table is stored;

(B) a color density measuring means for determining a combination of color densities of the object to be measured;

(C) second storage means for storing a combination of color densities obtained by the color density measurement means;

(D) The combination of the color density of the color density-dot area ratio conversion table stored in the first storage means and the color density of the DUT stored in the second storage means Are compared with each other, and the one closest to the color density combination of the measured object is selected from the color density combinations stored in the color density-dot area ratio conversion table. Color density selecting means,

(E) a combination of the selected color densities;
If the combination of the color densities of the object to be measured does not match, the combination of the dot area ratios is obtained by interpolation using a vector method based on the data in the color density-dot area ratio conversion table. Point area ratio interpolation means,

(F) a combination of the selected color densities;
If the combination of the color densities of the DUT does not match, the interpolated halftone dot area ratio is displayed, and if the two match, the halftone dot corresponding to the selected combination of color densities is displayed. Dot area ratio display means for displaying a combination of area ratios,

In the halftone dot area ratio determining apparatus having the above-mentioned means (a) to (f), the following means, namely,

(A) When replacing the gray component obtained by multiplying the three colors of Y, M and C with the Bk version,
The gray component obtained by multiplying the three colors C is replaced with the Bk version, and a combination of any two of the three colors Y, M, and C and Bk, that is, Y, M, Bk, M ,
Halftone dot area ratio determining means for obtaining a combination of halftone dot area percentages for each of the three types of C, Bk or C, Y, Bk;

(B) When the gray component obtained by multiplying the three colors of Y, M and C is replaced with the Bk version, the combination of the three colors shown in (a) above, ie, Y, M, Bk,
Halftone dot area ratio display means for displaying a combination of halftone dot area ratios of the respective plates in one of three ways of M, C, Bk or C, Y, Bk;

A dot area ratio determining apparatus characterized by having the above (a) to (b).

[0035]

The halftone dot area determining apparatus according to the present invention determines the optimum halftone dot area ratio of each color plate for a color sample of a printing material to be printed in order to prepare plates of each color to be actually printed. At the time of determination, not only the case of combining the plates of each color using a total of four colors of Y, M, C and Bk as printing inks, the operation mode is switched by simply operating the changeover switch with a simple one-touch operation. Even if the gray obtained by multiplying Y, M, and C as described above is replaced with Bk,
In the case of using an ink composed of a total of three colors of any two of the three colors Y, M, and C and Bk, the combination of the optimal halftone dot area ratios of the three color plates is determined by the color density. -Search for combination data while performing arithmetic processing based on the data in the dot area ratio conversion table, and also perform interpolation based on the data in the table if necessary, and determine the optimum combination of the determined dot area ratios through the display device. It is to display.

[0036]

【Example】

Embodiment 1 Next, the present invention will be described in more detail with reference to the drawings.

FIG. 7 is a schematic external view of a halftone dot area determining apparatus according to an embodiment of the present invention. Now,
FIG. 1 is a conceptual diagram of the apparatus of the present application. The first storage means 10 stores in advance a combination of a color density and a halftone dot area ratio corresponding to the combination of the color densities of a plurality of color separations. Is stored, and the color density combination data obtained by the color density measurement means 20 for obtaining the color density combination data of the measured object is the second color density-dot area ratio conversion table. The information is temporarily stored in the storage means 30.

As the combination data of the color densities stored in the second storage means 30, for example, three types of color densities of the object to be measured obtained through respective filters of an R filter, a G filter, and a B filter can be used. One set of combinations of color densities, and four types of color densities obtained by adding color densities obtained through, for example, an amber filter or an ND filter in addition to the above-described filters. Things.

Next, the color density selecting means 40 stores the combination of the color density in the color density-dot area ratio conversion table stored in the first storage means 10 and the color density in the second storage means 30. The color density is compared with a combination of the color densities of the object to be measured.
From the combinations of color densities in the halftone dot area ratio conversion table, the one closest to the combination of color densities of the measured object is selected.

The combination of the halftone dot area ratios corresponding to the color density combination selected from the color density / halftone dot area ratio conversion table as the one closest to the color density combination of the measured object is the halftone dot area ratio. After being appropriately interpolated by the interpolating means 60 by the vector method, the image is displayed by the dot area ratio displaying means 70.

In order to stabilize the color at the time of printing or to save the amount of ink used, if it is desired to replace the gray component by multiplying the three colors of Y, M and C with Bk, the dot area ratio Y, M, B by replacement means 80
After being replaced with any combination of dot area ratios of k, Bk, Y, C, or M, C, Bk, it is displayed by the dot area ratio display means 70. As described above, when the color of the object to be measured (for example, a color sample) is expressed by printing with printing ink, it is easy to determine what halftone dot area ratio the ink of each color should be overprinted.

[0042]

[Table 1]

[0043]

[Table 2]

(Table 1) and (Table 2) show an example of a color density-dot area ratio conversion table. On the left side, the values are obtained through an R filter, a G filter, a B filter, and an amber filter. The combinations of the color densities shown are shown on the right, and the combinations of the dot area ratios corresponding to the combinations of the color densities shown on the left are shown on the right.

Such a color density / halftone dot area ratio conversion table is created as follows. First, Y, M,
Using the respective inks of C and Bk, the dot area ratio is 0% to 1%.
Printing is actually performed by changing the interval up to 00% at appropriate intervals, for example, at 10% intervals as shown in (Table 1) and (Table 2) to create a color chart.

That is, in the example of (Table 2), the dot area ratios of the M, Y, and Bk plates are 0% for Nos. 1 to 11, and the C plate only changes by 10% between 0% and 100%. Let me
Also, for the numbers 12 to 22, the halftone dot area ratio of the Y and Bk plates is 0%, the halftone dot area ratio of the M plate is 10%, and only the C plate is 10%.
% To 100% are changed by 10%, and color charts are prepared by various combinations in which the halftone dot area ratio of each of the Y, M, C, and Bk plates is changed at intervals of 10%. .

[0047] Such combinations Y, M, C, results in a combined total of 11 ⁴ ie 14,641 ways by changing at 10% intervals dot percent for each version of four colors consisting of Bk.

A combination of the color densities obtained through the R filter, G filter, and B filter for each color of the color chart created as described above,
Alternatively, a combination in which a color density obtained through an amber filter or an ND filter is further added thereto is obtained. As described above, the color density-dot area conversion table showing the correspondence between the combinations of the color densities of the various colors and the combinations of the halftone area ratios of the corresponding color plates is created.

It is common to measure the color density using the R, G, B amber or ND filters described above, but an interference filter or the like having a peak in the absorption portion of the spectral reflection curve of the printing ink. There may be. The same filter as that used when creating the color density-dot area ratio conversion table must be used also when measuring the color density of the measured object.

Looking at the color density-dot area ratio conversion table obtained as described above, for example, in the case of numbers 1 to 11 in (Table 1), the dot areas of the M, Y, and Bk plates are shown. Although the ratio is 0% and does not change and only the C plate is changed, not only the color density through the R filter which is a complementary color of the C plate but also the other G, B and amber filters. All color densities have also changed. This is because the C ink contains not only the C component but also other color components.

This relationship is the same for other inks, and includes other components. Therefore, when determining the dot area ratio of an object to be measured, not only one filter but also the color density through another filter must be taken into consideration. The data of the color density / halftone dot area ratio conversion table is stored in the first storage means 10, and as such storage means, an appropriate one from among a magnetic disk, a floppy disk, a ROM and the like is used. .

As described above, the color density / dot area ratio conversion table is stored in the first storage means 10 in advance.

The color density measuring means 20 shown in FIG. 1 is for measuring the color density of an object to be measured, and FIG. 2 is a block diagram showing an embodiment thereof. In the example of FIG. 2, the DUT 1 such as a color sample is illuminated by a light source 21, and the reflected light is input to a photoelectric conversion element 23 via a filter 22 and is converted into an electric signal. The filter 22 is the same as that used when creating the color density-dot area ratio conversion table.
Three types of filters, a B filter, or four types of filters obtained by further adding an amber filter or an ND filter, and the like are mounted so as to be convertible. In this case, the conversion of the filter may be switched either electrically or manually. Further, in the example shown in FIG.
Although light is emitted from right above and light is received directly above, light may be emitted from directly above and light may be received in a 45 ° direction.

The electric signal generated by the photoelectric conversion element 23 is amplified by an amplifier 24, subjected to necessary correction by a correction circuit 25, subjected to logarithmic conversion by a logarithmic converter 26, and then converted to an analog signal by an A / D converter 27. Is converted into a digital signal, and is input to and stored in the second storage means 30 as a color density. The electric signal subjected to logarithmic conversion processing by the logarithmic converter 26 can be confirmed on a display meter 28. The display meter 28 may be provided after the A / D converter 27 so as to be digitally displayed.

As described above, the object to be measured is measured for each filter to obtain a combination of the color densities of the object to be measured, and these are stored in the second storage means 30 as described above. As the second storage means 30, a suitable one such as a RAM can be selected.

The color density selecting means 40 stores the combination of the color density of the measured object stored in the second storage means 30 and the first storage means 10.
Is compared with the combination of color densities in the color density-dot area ratio conversion table stored in the table. The closest one is selected, and the selection is performed as follows.

The color density obtained through each of the R, G, B, and amber filters of the device under test is represented by D _R. D _G. D _B. D _A , and the color density through the R filter, G filter, B filter, and amber filter shown at the number n in the color density-dot area ratio conversion table are each represented by T _R (n) , T
_{G (n), T B (} n), and T _A (n).

Next, the combination D _R of the color density of the measured object,
D _G, D _B, D _A and color density - combinations at the n-th number of the color density of the halftone dot area ratio conversion table T _R (n),
_{T G (n), T B} (n), the distance SA between T _A (n)
A combination of color densities T _R (n) such that (n) is minimized,
_{T G (n), T B} (n), obtaining the T _A (n).

The distance SA (n) is

[0060] [SA (n)] ² = [T _R (n) -D _R] ² + [T _G (n) -D _G] ² + [T _B (n) -D _B] ² + [T _A (n) -D _A] ²

It is obtained from the relational expression.

The number n at which the distance SA (n) is the minimum matches the number n at which the value of [SA (n)] ² is the minimum. Therefore, by using the above relational expression, the combination of the color densities in the color density-dot area ratio conversion table that minimizes the value of [SA (n)] ² is sequentially changed from n = 1 and searched. , N until the last number of n is obtained.

The combination of the color densities in the color density / halftone dot area ratio conversion table corresponding to the number n at which the value of SA (n) is the minimum is determined as the one closest to the color density combination of the measured object. And Y, M, C,
The combination of the halftone dot area ratios of each Bk plate is determined.

In this case as well, if [SA
(N)] If the value of ² becomes zero during the repetition of the above calculation and search, that is, the combination of the color density of the measured object and the color density / dot area ratio conversion table during the search. If a color density matching is found,
Since the combination of the halftone dot area ratios corresponding to the combination of the color densities at the value of n at that time is the data to be obtained, the subsequent search may be terminated.

Y, M, C, B determined as described above
The combination of the halftone dot area ratios of the respective k plates is displayed by the halftone dot area ratio display means 70 after being appropriately interpolated by the halftone dot area rate interpolation means 60 by the vector method. The dot area ratio display means can be appropriately selected from a printer, a CRT display, and the like.

The combination of the dot area ratios displayed as described above indicates the dot area ratio of each plate. If the combination of the dot area ratios thus obtained is used for printing with ink of each color, A printed matter that is the same as or similar to the color of the measured object can be obtained.

For example, if the 125th color density is selected as the color density closest to the combination of the color densities obtained by measuring the object to be measured, the C-plate is 30 from the table in (Table 2).
%, M version, 0%, Y version, 10%, and Bk version, 0% are selected. These halftone dot area ratios are appropriately interpolated by the halftone dot area ratio interpolation means 60 by the vector method. Is displayed by the halftone dot area ratio display means.

Therefore, by printing using the inks of the respective colors in the combinations indicated here, it is possible to obtain a printed matter which is the same as or close to the color of the measured object.

Incidentally, there is a case where the type of paper used for actually printing is different from the color chart paper used for preparing the data of the color density-dot area ratio conversion table. Alternatively, the solid density value used as a reference when creating the data of the color density / halftone dot area ratio conversion table is different from the solid density value used as a reference at the printing factory when printing is actually performed at the printing factory. In some cases.

In such a case, since the conditions for creating the color density / halftone dot area ratio conversion table are different from the conditions for actual printing, the color density / halftone dot area ratio conversion table is used. When comparing the combination of the color densities with the combination of the color densities of the object to be measured, the comparison must be made taking into account the difference in the above conditions.

An example of how such a difference in conditions is taken into account will be described below. However, it is very complicated to completely compensate for the difference in conditions. An example in which the correction is performed approximately is shown.

FIG. 3 is a graph for explaining the relationship between the color density and the halftone dot area ratio. For the sake of simplicity, they are described as having a linear relationship. May be applied to perform the correction.

In FIG. 4, when the color density-dot area ratio conversion table is prepared, a portion where only the C plate is 100% and all the other plates are 0% is obtained through an R filter having a complementary color relationship of C. color density that is is X _C, the color density obtained through the R filter paper part ink is not carried out at all in the all versions 0% i.e. color chart and was N _C.

Further, solid printing is performed in advance on a sheet to be actually printed using a C-plate at a density determined as a reference solid density at a printing factory and using a halftone dot area ratio of 100%. C applied to the paper to be actually printed
The color density obtained by measuring the solid density of the plate via the R filter with the apparatus of the present invention is X _C ′, and the color density of the unprinted paper measured via the R filter using the apparatus of the present invention Is N _C ′.

In FIG. 4, a straight line (a) and a straight line (b)
Indicates the relationship between the color density and the halftone dot area ratio when the color density / halftone dot area ratio conversion table is created and when printing is actually performed.

In this case, assuming that an object to be measured such as a color sample has a color density D _C ′ obtained through an R filter using the apparatus of the present invention, a halftone dot is obtained without any correction. When the area ratio is obtained, the dot area ratio P 'is obtained. However, in this case, a value different from the dot area ratio P to be actually obtained is obtained.

Therefore, in order to correct the error in this case, the color density value of the measured object is corrected as follows. That is, when the color density after correcting the value of the color density D _C ′ obtained by measuring the object to be measured through the R filter is defined as D _C ,

[0078]

The color density of the measured object obtained through the R filter is corrected by the relational expression.

Similarly, the color density of each of the M-plate only printed at 100%, the Y-plate only printed at 100%, and the Bk-plate printed only at 100% is obtained through the G filter, the B filter and the amber filter. And the G of the paper itself
The color density obtained through the filter, the B filter, and the amber filter is obtained in advance, and the color density obtained from the DUT through the G filter, the B filter, and the amber filter (or the ND filter) using the color density data is obtained. Make the correction,
Combinations of color densities D _C , D _M , D after each correction
_Y and _DBk are used for comparison with a combination of color densities in a color density-halftone dot area ratio conversion table.

That is, when performing the correction in this example, first, the color density of the paper for actually performing printing is obtained through the R, G, and B filters using the apparatus of the present invention. In addition, the reference solid printing section of each color ink in the printing factory is further processed by the apparatus of the present invention using an R filter for C ink, a G filter for M ink, a B filter for Y ink,
For the Bk ink, the color density measured through an amber filter is determined in advance.

These data are stored in the apparatus of the present invention. Next, the object to be measured is subjected to R, G,
The color density measured through each of the B and amber filters is corrected using the previously determined color density of the paper and the color density value of the reference solid printing unit.

In the correction example described above, the color density of the paper used for actual printing and the color density of the solid printing portion of each color ink are actually measured by the apparatus of the present invention to obtain correction data. However, when these data are obtained in advance or the like, the data may be input using ten keys or the like.

As still another correction method, the light portion and the shadow portion are R, G,
When a densitometer that can be independently adjusted for each of the B and amber filters is employed, the following may be adopted.

That is, the light portion measures the unprinted portion of the paper to be actually printed, and sets C, M, Y, and Bk of the color density-dot area ratio conversion table to 0% ( The density through each of the R, G, B, and amber filters is adjusted so that the color density of (in the case of the combination of number 1 in Table 1) is obtained, and the shadows of the sheets C and M to be printed are adjusted. , Y, and Bk, each of which has been printed at a solid density as a reference, and the solid density portion of the C ink is measured through an R filter, and the color density of the shadow portion at this time is measured. When the C of the density-dot area ratio conversion table is 100% (in the case of No. 11 in Table 1), the color density of the R filter is adjusted so that the M ink, the Y ink and the Bk ink are similarly adjusted. Also G filter, B
Color density measured through filter and amber filter-
Each of Y, M, and Bk in the dot area ratio conversion table is 1
Adjustment is made so that the color density of the G filter, B filter, and amber filter in the case of 00% is obtained.

After the adjustment as described above, the actual measurement of the object to be measured is performed, and the combination of the dot percentages is obtained.

The various correction methods have been described above.
In each case, 100% correction cannot be performed.

By the way, in normal printing, since there are many fluctuation factors such as the amount of ink, the amount of fountain solution, and the emulsification of ink, the print density of each of Y, M, C, and Bk varies. When viewed in a single color, even if the variation is acceptable, the variation in color can be clearly seen when multiplied by two or more colors.

In particular, gray produced by multiplying three colors of Y, M, and C is often replaced with Bk in general printing because the variation in color is easily recognized by human eyes. This operation has the effect of reducing variations in print quality and reducing the amount of ink used.

The present invention reduces the variation in the color of such a printed material, and replaces any one of Y, M, and C with Bk to obtain Y, M, Bk, Bk, Y, C, M, C, and C. It is an object of the present invention to provide an apparatus capable of determining any combination of dot area ratios of Bk.

That is, the invention of this application provides a color density-dot area ratio showing a correspondence relationship between a combination of color densities and a combination of halftone dot areas corresponding to the color density combinations of a plurality of color separations. A first storage unit in which a conversion table is stored; a color density measurement unit for obtaining a combination of color densities of the device under test; and a second storage unit for storing the color density combination obtained by the color density measurement unit. A combination of the color density of the color density-halftone dot area ratio conversion table stored in the first storage means and the combination of the color density of the DUT stored in the second storage means. Color density selecting means for comparing the color density to the halftone dot area ratio conversion table and selecting the color density combination closest to the color density combination of the measured object; and the color density combination described above. And the combination of the color density of the DUT match If not, a dot area ratio interpolating means for obtaining a combination of dot area ratios interpolated by the vector method based on the color density-dot area ratio conversion table, and multiplication of three colors of Y, M and C Is replaced by Bk, and Y, M, Bk, Bk, Y,
Means for determining a combination of halftone dot area ratios of C, M, C, and Bk; and, when the combination of the selected color density and the combination of the color densities of the device under test do not match, the interpolation is performed. The halftone dot area ratio is displayed, and when they match, the combination of the halftone dot ratios corresponding to the selected combination of color densities is displayed, and the gray component obtained by multiplying the three colors of Y, M, and C is displayed. Is replaced with Bk, Y, M, B
a dot area ratio display means for displaying any combination of dot area ratios of k, Bk, Y, C, M, C, and Bk.

Hereinafter, the gray component obtained by multiplying the three colors of Y, M and C is replaced with Bk, and Y, M, Bk,
The means for determining a combination of halftone dot area ratios of Bk, Y, C, M, C, and Bk will be described in further detail.

First, in the first storage means 10 in which the color density / dot area ratio conversion table is stored, substantially three of Y, M, Bk, Bk, Y, C and M, C, Bk are stored.
A color density / halftone dot area ratio conversion small table consisting of only combinations is set.

That is, a table group consisting of three types of combinations having elements of C = 0%, M = 0% or Y = 0% in the color density-dot area ratio conversion table is set and used. The color density measurement means 20, the second storage means 30, and the color density selection means 40 convert the color density combination closest to the color density combination of the measured object into the above three types of color density / halftone dot area ratio conversion tables. Choose from a group.

According to the combination of the selected color densities, Y, M, Bk, M, C, Bk or C, Y, Bk
Which combination is to be determined.

If the combination of the color densities selected here is the distance SA (n) = 0, that is, if it is selected as a case where the combination of the color densities of the object to be measured is completely matched, The combination of the halftone dot area ratios may be displayed on the halftone dot area ratio display means 70 as it is.

However, if the selected combination of color densities is selected in a case other than SA = O, the halftone dot area ratio for this selected combination of color densities is replaced by the halftone dot area ratio replacement means. Interpolation is performed within 80 to obtain a combination of dot area ratios that can print colors closer to the color of the device under test.

First, as shown in (Table 1) and (Table 2), C = 0%, M = 0%, Y = From the three types of table groups of 0%, the combination d (D _x , D _x
y , D _A ) is selected, the combination of the color densities is t (T _x , T _y , T _A ), and the combination of the halftone dot area ratios corresponding thereto is P (x, y, bk). And

In the following description, for clarity of explanation, Bk, excluding Y, is used as a combination of dot area ratios.
Although the description is limited to three colors of M and C, interpolation can be performed in exactly the same manner when C or M is removed.

FIG. 4 is an explanatory diagram of the interpolation method.
G, represent each A axis R, G, combinations t of color density color density obtained through the filter _{A (T R, T G,} T A) as the origin. here,

[0101]

(Equation 1)

Is set,

B _R = D _R -T _R , B _G = D _G -T _G and B _A = D _A -T _A

Is obtained.

One unit (10% in the case of (Table 1) and (Table 2)) for each combination P (c, m, bk) of the halftone dot area ratio corresponding to the combination t of the color density. P ₃ (c ± 10, m ± 10, bk)
± 10), and the corresponding color density combination t ₃
(TR ₃ , _{TG 3} , TA ₃ ) can be known from the color density-dot area ratio conversion table. The halftone dot area ratio P
₃ Whether (c ± 10, m ± 10, bk ± 10) should be positive or negative

[0106]

(Equation 2)

It is determined whether each of the components is greater than or equal to zero or smaller than zero.
If it is smaller than zero, it is negative.

In this case, the code to be employed for each of c ± 10, m ± 10 and bk ± 10 is determined by the respective codes of B _R , B _G and B _A. here,

[0109]

(Equation 3)

Given the following,

[0111]

(Equation 4)

Can be expressed as a composite of several vectors. For the sake of simplicity,

[0113]

(Equation 5)

In the following description, it is assumed that each component is greater than zero.

The combination P (c, m, b) of the halftone dot area ratios
The combinations of the dot percentages when the bk component is increased by 10% with respect to k) and when the bk component and the m component are each increased by 10% are represented by P ₁ (c, m, b), respectively.
k + 10) and P ₂ (c, m + 10, bk + 10).

The combinations of the color densities corresponding to the combinations of the dot area ratios P ₁ and P ₂ are respectively represented by t ₂ (TR ₁ , _{TG 1} , T _{A 1} ) and T ₂ by the color density-dot area ratio conversion table. t
₂ (TR ₂ , _{TG 2} , TA ₂ ). Therefore,

[0117]

(Equation 6)

Is

[0119]

(Equation 7)

By the following,

[0121]

(Equation 8)

It can be expressed as Therefore,

[0123]

(Equation 9)

Is

[0125]

(Equation 10)

By the following,

[0127]

[Equation 11]

Is represented as here,

[0129]

(Equation 12)

Since each component is known as described above, α, β, and γ are obtained from the above relational expressions.

When calculating the dot area ratio including Bk, it is necessary to pay attention to the following points.

[0132] That of the concentration increasing the dot percentage of Bk D _A component rises at the same time D _R of, D _B, is that D _G component is increased. That is, the axis of A is (FIG. 5)
Actually, as shown in FIG.
It is inclined at an angle of 5 °. Therefore, when calculating the combination P '(c', m ', bk') of the interpolated halftone dot area ratios, take this into account.

[0133]

(Equation 13)

It is necessary to take into account the effects of Therefore, the combination P (c, m, bk) of the halftone dot area ratio corresponding to the color density combination t selected as the closest to the color density combination d (D _R , D _G , D _A ) of the DUT. Of the dot area ratios P ′ (c ′, m ′, bk ′) obtained by interpolating the values in Tables 1 and 2 are at 10% intervals.

B ′ _k = b _k + α × 10

[0136]

[Equation 14]

[0137]

(Equation 15)

Is obtained.

As described above, the gray component obtained by multiplying the three colors of Y, M, and C is replaced with B _k , and the interpolated halftone dot area combination P ′ (c ′, m ′, bk) ')
Is determined. In addition,

[0140]

(Equation 16)

There are various other methods of expressing a vector as a combination of other vectors, and any vector may be used. However, in order to obtain a proper interpolation value, as shown in FIG. 4, a vector obtained by connecting the color density combinations obtained from the color density-dot area ratio conversion table reaches the color density combination t ₃ . It is preferable to select the vector as follows. When a combination of dot area ratios including b _k is obtained, as shown in FIG.

[0142]

[Equation 17]

It is easier to obtain a reasonable interpolation value by taking the value in the A-axis direction.

When the combination of the color densities in the color density-dot area ratio conversion table completely matches the combination of the color densities of the device under test, the halftone dot area display means 70 displays the matched color densities. Display the combination of dot area ratios corresponding to the combination of
If they do not completely match, the combination of the halftone dot area ratios interpolated as described above is displayed.

When the gray component obtained by multiplying the three colors Y, M, and C is replaced with Bk, a combination of three colors, that is, Y, M, Bk, M, C, Bk, or C, Y, Bk is used. Is displayed.

FIG. 6 is a flowchart showing how a combination of halftone dot area ratios is determined using the apparatus according to the present invention described above.

[0147]

Since the present invention has the above-described configuration, the halftone dot area determining apparatus according to the present invention has the following effects.

First, even when a color to be reproduced by printing, such as a color sample, is designated by an actual color, the designation can be made very easily and in a short time even by an inexperienced person. The halftone dot area ratio of the halftone positive of each color for reproducing the different colors can be obtained.

Next, since the halftone dot area ratio of the halftone positive of each plate is always obtained in a standardized form, unlike the conventional method judged by humans, the quality of printed matter can be easily managed.

In order to stabilize colors at the time of printing,
In order to save the amount of ink used, the gray component obtained by multiplying the three colors of Y, M, and C is replaced with a Bk plate.
Color combinations, ie, Y, M, Bk, M, C, Bk,
Alternatively, it can be converted to a combination of any one of C, Y, and Bk.

Further, in addition to the above-described effects, a more accurate combination of dot area ratios can be obtained very easily.

Further, the processing time required for the interpolation for obtaining the combination of the dot areas with high precision can be greatly reduced.

[0153]

[Brief description of the drawings]

FIG. 1 is an explanatory diagram showing a conceptual diagram of an embodiment of a halftone dot area ratio determining apparatus according to the present invention.

FIG. 2 is an explanatory diagram showing a color density measuring means of one embodiment of a halftone dot area ratio determining apparatus according to the present invention.

FIG. 3 is a schematic graph for explaining the relationship between the color density and the dot area ratio in one embodiment of the dot area ratio determination device according to the present invention.

FIG. 4 is an explanatory diagram showing a method of halftone dot area interpolation processing in one embodiment of the halftone dot area ratio determining apparatus according to the present invention.

FIG. 5 is an explanatory diagram showing a method of interpolation processing of a dot area ratio in one embodiment of the dot area ratio determining apparatus according to the present invention.

FIG. 6 is a flowchart showing a schematic algorithm of the embodiment of the halftone dot area determining apparatus according to the present invention when determining a combination of halftone area ratios.

FIG. 7 is an explanatory diagram showing an outline appearance of an embodiment of a halftone dot area determining apparatus according to the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... Measurement object 10 ... First memory means 20 ... Color density measuring means 21 ... Light source 22 ... Filter 23 ... Photoelectric conversion element 24 ... Amplifier 25 ... Correction circuit 26 Logarithmic converter 27 A / D converter 28 Display meter 29 Signal cable 30 Second storage unit 40 Color density selection unit 60 Halftone dot area interpolation means 70 ・ ・ ・ Halftone dot area ratio display means 80 ・ ・ ・ Halftone dot area ratio replacement means

──────────────────────────────────────────────────続 き Continuation of the front page (72) Inventor Kazuo Yarita 1-5-1, Taito, Taito-ku, Tokyo Toppan Printing Co., Ltd. Examiner Yujiro Yamaga (56) References JP-A-61-123845 (JP, A) JP-A-4-31859 (JP, A) JP-A-3-175452 (JP, A) JP-A-63-35078 (JP, A) JP-A-62-191641 (JP, U) (58) (Int.Cl. ⁶ , DB name) G03F 5/00-5/24

Claims (1)

(57) [Claims] 1. An apparatus for determining a dot area ratio which will be described below: (a) between a combination of color densities and a combination of dot area ratios corresponding to the color density combinations of a plurality of color separations of,
First storage means for storing a color density-halftone dot area ratio conversion table indicating a correspondence relationship, (b) color density measurement means for obtaining a combination of color densities of a device under test, and (c) color density measurement Second storage means for storing a combination of color densities obtained by the means, (d) a combination of color densities in a color density-dot area ratio conversion table stored in the first storage means; A comparison is made between the combination of the color density of the object to be measured stored in the second storage means, and the one closest to the combination of the color densities of the object to be measured is determined by the following equation. A color density selecting means selected from the combinations of color densities stored in the rate conversion table; (e) when the selected combination of color densities does not match the color density combination of the object to be measured Is a combination of the dot area ratio, the color density−the dot area ratio A halftone dot area ratio interpolating means obtained by interpolation using a vector method based on the data in the conversion table; (f) the combination of the selected color density does not match the color density combination of the device under test; in case of,
A halftone dot area ratio display means for displaying the interpolated halftone dot area ratios and, if they match, displaying a combination of halftone dot area ratios corresponding to the selected combination of color densities; In the halftone dot area ratio determining apparatus having the means of (f) to (f), the means described below: (a) Y, M,
When the gray component obtained by multiplying the three colors C is replaced with the Bk version, the gray component obtained by multiplying the three colors Y, M, and C is replaced with the Bk version. A combination of any two colors and Bk, that is, Y, M, Bk, M, C, Bk or C, Y, Bk
A dot area ratio determining means for obtaining a combination of the dot area ratios of the respective plates according to any one of the following three methods. , The combination of the three colors shown in (a) above, ie, Y,
Halftone dot area ratio display means for displaying a combination of halftone dot area ratios of each of the three versions of M, Bk, M, C, Bk or C, Y, Bk. A dot area ratio determination device, comprising: