JPH0520731B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention provides C (cyan), M
This invention relates to a device for determining the halftone dot area ratio of each plate (magenta), Y (yellow), and Bk (black).

Conventionally, a large number of color samples for specifying colors may be attached to printing layout sheets. For example, if you want to uniformly fill the background with a certain color, a small piece of paper with the background color is attached as a color sample.

When printing a specified area with the same color as this color sample, to determine what halftone area ratio to print each CMYBk plate, use this color sample and 10%.
The most similar color chart is visually compared with the printed color chart with the dot area ratio changed according to the interval, and the selected color is determined by the percentage of the dot area ratio of each plate. Generally speaking, it is determined by using what is written in the color chart. However, this method has the disadvantage that it takes time to make the comparison, and the colors selected from the color chart vary depending on the person, so that the determined halftone area ratio tends to vary. Accurately specifying the dot area ratio requires an experienced veteran, but even then it is not perfect.

On the other hand, reflection densitometers that can measure the density of an object to be measured and calculate the dot area ratio are currently on the market. In this densitometer, the measured density value is processed by a microcomputer built into the densitometer to calculate the 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, measure the standard density in advance and set the halftone area ratio of that part to the standard value (100%).
It is necessary to set the dot area ratio to , then actually measure the object to be measured for the dot area ratio, and use the relationship with the reference density.

Therefore, it is only applicable to colors that have a standard density, and is usually used only for monochrome colors. Moreover, the Yule-Nielsen equation can be established by ideally reproducing halftone dots without dot gain, and by appropriately setting coefficients that vary depending on the screen frequency, density, and paper transparency. Therefore, in actual use, it is not possible to accurately obtain a wide range of dot area ratios from light areas to shadow areas even in monochromatic areas. Furthermore, it is extremely difficult to calculate the dot area ratio of secondary colors or higher.

Therefore, such a densitometer cannot display the combination of halftone surface forces for each version of YMCBk to express the color of the color sample.

Further, such conventionally known densitometers cannot display the combination of dot area ratios for each YMCBk version for the following reason. In other words, printing ink
YMC ink is not ideal; Y ink contains M and C components, M ink contains Y and C components, and C ink contains M and Y components. Contains ingredients. Since the YMC printing ink actually used is not ideal, the colors of the objects to be measured such as color samples are B (blue violet), G (green), and R (red), which are complementary colors of YMC. Even if you calculate the dot area ratio using the Yule-Nielsen formula from the density values obtained by measuring through each filter, the value will not match the actually required dot area of each positive YMC. It does not indicate the percentage.
This will be more clearly understood by the following example. For example, it is easy to understand if we assume that an image with a halftone dot area ratio of 100% is printed using only C ink from a certain ink manufacturer. If we calculate the density of this printed matter through an R filter, a G filter, and a B filter, the density will be 1.53, 0.52, and 0.17, respectively.
These values are C, which is a complementary color of RGB.
It is clear that it cannot be used to calculate the halftone area ratio of the MY version. This becomes even more complicated when not only one color of ink but a plurality of color inks are to be overprinted.

The present invention eliminates the various drawbacks described above, and when expressing any color using ink of each YMC color or each color of YMCBk, it is possible to determine the dot area ratio of each color plate. The purpose is to provide a device that can easily determine which combinations should be used.

That is, the invention of this application stores a color density-dot area ratio conversion table showing the correspondence between a combination of color densities and a combination of dot area ratios corresponding to the combinations of color densities of color separation plates of a plurality of colors. being the first
a color density measuring means for determining the combination of color densities of the object to be measured; a second storing means for storing the combination of color densities determined by the color density measuring means; The combination of color densities in the color density-dot area ratio conversion table stored in the storage means is compared with the combination of color densities of the object to be measured stored in the second storage means to determine the color density-dot area ratio. a color density selection means for selecting the color density combination closest to the color density combination of the object to be measured from among the color density combinations in the point area ratio conversion table; and a color density selection means corresponding to the color density combination selected by the color density selection means. The present invention relates to a halftone dot area ratio determining device characterized by comprising a halftone dot area ratio display means for displaying a combination of halftone dot area ratios, and further comprising: a halftone dot area ratio display means for displaying a combination of halftone dot area ratios, and further detailed The present invention aims to provide a device that can obtain a combination of dot area ratios.

Next, the present invention will be explained in more detail with reference to the drawings.

FIG. 1 is a conceptual diagram of the device of this application.
The storage means 10 stores in advance a color density-dot area ratio conversion table showing the correspondence between combinations of color densities and combinations of dot area ratios corresponding to the combinations of color densities of color separation plates of a plurality of colors. The color density combination data obtained by the color density measuring means 20 for obtaining the color density combination data of the object to be measured is temporarily stored in the second storage means 30. As the color density combination data stored in the second storage means 30, for example, three types of color density obtained by passing the color density of the object to be measured through each of the R filter, G filter, and B filter are used. A combination of four types of color densities, or a combination of four types of color densities obtained by adding color densities obtained through an amber filter or an ND filter in addition to each of the above-mentioned filters. . Next, the color density selection means 40 selects the color density combination of the color density-dot area ratio conversion table stored in the first storage means 10 and the object to be measured stored in the second storage means 30. A combination of color densities close to that of the object to be measured is selected from among the combinations of color densities in the color density-dot area ratio conversion table.

In this way, the combination of dot area ratios corresponding to the combination of color densities selected from the color density-dot area ratio conversion table as the one closest to the combination of color densities of the object to be measured is determined by the dot area ratio interpolation means. After being subjected to appropriate interpolation using a vector method by 60, it is displayed by halftone area ratio display means 70. As described above, when expressing the color of an object to be measured (for example, a color sample) by printing with printing ink, it is easily determined at what halftone area ratio each color of ink should be printed.

Figures 2a and b show an example of a color density-dot area ratio conversion table, and the left side shows the combinations of color densities obtained through each of the R filter, G filter, B filter, and amber filter. is shown, and on the right side, combinations of halftone area ratios corresponding to the combinations of color densities shown on the left side are shown.

Such a color density-dot area ratio conversion table is created as follows. First, YM on printing paper
Using each ink of C.Bk, halftone area ratio 0%
to 100% at appropriate intervals, for example at 10% intervals as in the case of FIG. 2, and actually prints to create a color chart. That is, in the example in Figure 2, for numbers 1 to 11, the MYBk version has a halftone area ratio of 0%, and only the C version has a dot area ratio of 0% to 100%, varying in 10% increments, and for numbers 12 to 11, the dot area ratio is 0%. number 22
Until now, the dot area ratio was 0% for the Y.Bk version, 10% for the M version, and the dot area ratio was between 10% and 100% for the C version only.
The dot area ratio of each plate of YMCBk was changed in 10% increments, and color charts were created using various combinations. Such combinations result in 11 ⁴ =14641 combinations when the dot area ratio is varied at 10% intervals for each version of YMCBk.

Combinations of color densities obtained for each color of the color chart created as described above through each filter, R filter, G filter, B filter, or further through an amber filter or ND filter. Find the combination that adds the resulting color density. As described above, a color density-dot area ratio conversion table is created that shows the correspondence between combinations of color densities and corresponding combinations of halftone area ratios of plates of each color for various colors.

Although color density is generally measured using the RGB amber or ND filters described above, an interference filter or the like having a peak in the absorption portion of the spectral reflection curve of the printing ink may also be used. The same filter used when creating the color density-dot area ratio conversion table must be used when measuring the color density of the object to be measured.

Looking at the color density-dot area ratio conversion table obtained as above, for example, from number 1 to number 11 in Figure 2, the dot area ratio of each version of MYBk remains 0% and does not change. Although only the C version has changed, not only the color density through the R filter, which is the complementary color of C, but also the color density through the other GB amber filters has changed. This is because the C ink contains not only the C component but also other color components.

This relationship holds true for other inks as well, and they contain other components. Therefore, when determining the dot area ratio of a certain object, it is necessary to take into account not only the color density through one filter but also the color density through other filters. The data of the color density-dot area ratio conversion table is stored in the first storage means 10, and such storage means may be a magnetic disk, a floppy disk,
An appropriate device such as ROM 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 measures the color density of the object to be measured, and FIG. 3 is a block diagram showing one embodiment thereof. In the example shown in FIG. 3, the object 1 to be measured, 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, where it is converted into an electrical signal. The filter 22 is the same as that used when creating the color density-dot area ratio conversion table, and includes an R filter, a G filter,
Three types of B filters or four types of filters, including an amber filter or ND filter, are installed in a convertible manner. In this case, the filter may be switched electrically or manually. In addition, in the example shown in Figure 3, the light from the light source is irradiated from an angle of 45 degrees,
Although the light is received directly above, it is also possible to emit light from directly above and receive the light at a 45° angle. The electrical 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 processing by a logarithmic converter 26, and then converted from an analog signal to a digital signal by an A/D converter 27. is converted into a color density, and is input and stored in the second storage means 30 as a color density. Note that the value of the electrical signal subjected to logarithmic conversion processing by the logarithmic converter 26 can be checked on a display meter 28.
The display meter 28 is an A/D converter 27.
It may also be displayed digitally by placing it after the .

As described above, the object to be measured is measured for each filter to obtain a combination of 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, an appropriate one such as a RAM can be selected.

The color density selection means 40 selects a combination of color densities of the object to be measured stored in the second storage means 30 and a combination of color densities in the color density-dot area ratio conversion table stored in the first storage means 10. The combination of color densities closest to the color density of the object to be measured is selected from among the combinations of color densities in the color density-dot area ratio conversion table.The selection is performed as follows. It will be done. The color densities obtained through the R filter, G filter, B filter, and amber filter of the object to be measured are D _R , D _G , D _B , D _A
and the R filter at the nth number of the color density-dot area ratio conversion table, G
The color density through the filter, B filter, and amber filter are T _R (n), T _G (n), T _B (n), respectively.
Let T _A (n). Next, the combination of color densities of the object to be measured D _R ,
Combination of D _G , D _B , D _A and the nth color density of the color density-dot area ratio conversion table T _R (n), T _G
Combination of color densities T _R (n), T _G (n), T _B (n) that minimizes the distance SA(n) between (n), T _B (n), T _A (n) , find T _A (n). The distance SA(n) is [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 ] It is obtained from the relational expression of ² .

The value of n that minimizes the distance SA(n) matches the value of n that minimizes [SA(n)] ² . Therefore, using the above relational expression, find the combination of color densities in the color density-dot area ratio conversion table that minimizes [SA(n)] ² as n=
By sequentially changing the value of n from 1 to the end and searching, the value of n that minimizes SA(n) can be found.
determining the combination of color densities in the color density-dot area ratio conversion table corresponding to n that minimizes SA(n) as the one closest to the combination of color densities of the object to be measured;
A combination of halftone area ratios of each YMCBk plate corresponding to the combination of color densities is determined.

Even in this case, if [SA(n)] ² becomes zero during the search, the combination of color densities of the object to be measured and the color in the color density-dot area ratio conversion table If a matching density is found, the combination of halftone area ratios corresponding to the combination of color densities at the current value of n is the data to be sought, and the subsequent search may be discontinued.

The combination of dot area ratios of each version of YMCBk determined in the above manner is subjected to appropriate interpolation using a vector method by the dot area ratio interpolation means 60, and then displayed by the dot area ratio display means 70. Ru. Printers and display tubes are used as a means of displaying the dot area ratio.
An appropriate device such as a CRT display can be adopted.

The combination of halftone dot area ratios displayed as above indicates the halftone dot area ratio of each plate, and depending on the combination of halftone dot area ratios obtained in this way, printing using ink of each color will result in a It is possible to obtain a printed matter with the same or similar color to the measured object. For example, if the 125th color density is selected as the color density closest to the combination of color densities obtained by measuring the object to be measured, then from the table in Figure 2, the C version is 30%, and the M version is 0.
%, 10% for the Y version, and 0% for the Bk version, and these halftone dot area ratios are determined by the halftone dot area ratio after being appropriately interpolated by the vector method by the halftone area ratio interpolation means 60. Displayed by area ratio display means. Therefore, by printing using ink of each color in the combination shown here, it is possible to obtain a printed matter that is the same as or similar to the color of the object to be measured.

Incidentally, the type of paper for the color chart used to create the data of the color density-dot area ratio conversion table may be different from the type of paper used for actual printing. Or, if the solid density value used as the standard when creating the data of the color density-dot area ratio conversion table is different from the solid density value used as the standard at the printing factory when actually printing at that printing factory. In some cases, it may be. In such cases, the conditions for creating the color density-dot area ratio conversion table and the conditions for actual printing are different, so the color density of the color density-dot area ratio conversion table is When comparing the combinations of color densities of the objects to be measured and the combinations of the color densities of the objects to be measured, the differences in the conditions described above must be taken into consideration.

An example of how to take such a difference in conditions into consideration is explained below, but since it would be very complicated to completely compensate for the difference in conditions, in the example below, A case of approximate correction is shown.

Figure 4 is a graph for explaining the relationship between color density and halftone area ratio.For simplicity, we will explain this as a linear relationship, but the same idea can be applied to curves. All you have to do is make a correction.

In Figure 4, when creating the color density-dot area ratio conversion table, the density obtained through the R filter, which is the complementary color of C, is changed to the part where only the C plate is 100% and all other plates are 0%. Assume that the density of all the plates is 0%, that is, the color density obtained through the R filter on the portion of the color chart paper where no ink is applied is _{N C.} In addition, solid printing is performed in advance on the actual paper to be printed using a C plate with a density determined as a standard solid density at the printing factory and a plate having a halftone dot area ratio of 100%. The solid density of the C plate applied to the paper to be actually printed is evaluated using the apparatus of the present invention.
The color density measured through the filter is X _C ', and the color density obtained by measuring the unprinted paper through the R filter using the apparatus of the present invention is N _C '. shall be. In FIG. 4, straight lines a and b indicate the relationship between color density and halftone dot area ratio when creating a color density to halftone dot area ratio conversion table and when actually printing. In this case, the color density obtained by passing the object to be measured such as a color sample through an R filter using the apparatus of the present invention is
If D _C ′, then the dot area ratio P′ for calculating the dot area ratio can be obtained without any correction, but it is possible to obtain a correction different from the dot area ratio P that should actually be calculated. I end up getting beaten up. Therefore, in order to correct the error in this case, the color density value of the object to be measured is corrected as follows. In other words, the object to be measured is R
Color density measured through a filter
When the color density after correcting the value of D _C ′ is D _C , the relational expression D _C = (D _C ′−N _C ′)+X _C −N _C /X _C ′−N _C ′+N _C The color density of the object to be measured obtained through the R filter is corrected. In the same way, the color density of the M plate only printed at 100%, the Y plate only printed at 100%, and the Bk plate only printed at 100% is determined through the G filter, B filter, and amber filter, and then Obtain the color density of the paper itself through the G filter, B filter, and amber filter, and use these color density data to obtain the measured object through the G filter, B filter, and amber filter (or ND filter). The corrected color densities are also corrected, and the corrected color density combinations D _C , _DM , _DY , D _Bk are compared with the color density combinations in the color density-dot area ratio conversion table. used for That is, when performing correction in this example, first, the color density of the paper to be actually printed is determined using the apparatus of the present invention through R, G, and B filters. Furthermore, the standard solid printing area of each color ink at the printing factory is measured using the apparatus of the present invention, and the C ink is R.
The color densities are measured through a G filter for M ink, a B filter for Y ink, and an amber filter for Bk ink. These data are stored in the device of the present invention. Next, the color density of the object to be measured is measured using the apparatus of the present invention through R, G, B, and amber filters. Correction is performed using density.

In the example of correction described above, the color density of the paper used for actual printing and the color density of the solid printed area of each color ink were actually measured using the apparatus of the present invention to obtain correction data. In cases where the data has been obtained in advance, the data may be input using a numeric keypad or the like.

Furthermore, as another correction method, as a color density measuring means, the light part and the shadow part are R, G,
If a densitometer that can be adjusted independently for each of the B and amber filters is used, the following procedure may be used. In other words, the light section measures the unprinted part of the paper to be printed,
Color density-dot area ratio conversion table C, M, Y,
Each of Bk is 0% (in case of number 1 in Figure 2)
Adjust the density through R, G, B, and amber filters so that the color density becomes Prepare a print with density, and use R for the solid density part of C ink.
The color density of the shadow area at this time is measured through a filter, and the color of the R filter is calculated when C in the color density-dot area ratio conversion table is 100% (in the case of number 11 in Figure 2). Similarly, M ink, Y ink, and Bk ink are measured through G filter, B filter, and amber filter, and Y, M, and Bk in the color density-dot area ratio conversion table are adjusted. Adjust so that the color density of the G filter, B filter, and amber filter is the same as when each is 100%. After making the adjustments in this way, the actual object to be measured is measured to determine the combination of dot area ratios.

Although various correction methods have been described above, none of them can provide 100% correction.

The accuracy of the dot area ratio determined as described above depends on the accuracy with which the dot area ratio is created in the color density-dot area ratio conversion table. In the example shown in FIG. 2, the dot area ratio is changed at 10% intervals, so the accuracy is up to 10%.

Therefore, if a more accurate halftone area ratio is required, it is sufficient to create a color density to halftone area ratio conversion table with the required accuracy.
In this case, the amount of data in the color density-dot area ratio conversion table becomes extremely large, and creating such data not only requires a great deal of time and effort, but also requires a storage device with a large storage capacity. This method has the disadvantage that it takes a long time to compare and calculate the measurement data of the object to be measured.

The invention of this application eliminates such drawbacks and
It is an object of the present invention to provide an apparatus that can determine halftone dot area ratios at intervals finer than data intervals of halftone dot area ratios in a color density-dot area ratio conversion table.

That is, the invention of this application provides a color density-dot area ratio conversion table showing the correspondence between a combination of color densities and a combination of dot area ratios corresponding to the combinations of color densities of color separation plates of a plurality of colors. a first storage means for storing color density combinations; a color density measurement means for determining the combination of color densities of the object to be measured; and a second storage means for storing the combinations of color densities determined by the color density measurement means.
a combination of color densities of the color density-dot area ratio conversion table stored in the first storage means and a combination of color densities of the object to be measured stored in the second storage means; color density selection means for comparing the combinations of color densities in the color density-dot area ratio conversion table to select the combination of color densities closest to the combination of color densities of the object to be measured; If the combination does not match the combination of color densities of the object to be measured, a dot area ratio interpolation unit obtains a combination of dot area ratios interpolated by a vector method based on the color density-dot area ratio conversion table. and,
If the selected combination of color densities and the combination of color densities of the object to be measured do not match, the interpolated halftone area ratio is displayed, and if they match, it corresponds to the selected combination of color densities. and a halftone dot area ratio display means for displaying combinations of halftone dot area ratios.

The interpolation means will be explained in more detail below.

First, there is a first storage means 10 in which a color density-dot area ratio conversion table is stored, and a color density measuring means 2.
0. The second storage means 30 and the color density selection means 40 select the color density combination closest to the color density combination of the object to be measured from the color density-dot area ratio conversion table.

If the combination of color densities selected in this way is selected as a result of the distance SA=0, that is, if it is selected as a result of completely matching the combination of color densities of the object to be measured, then the corresponding halftone area ratio It is sufficient to display the combinations as they are on the dot area ratio display means 70. However, if the selected combination of color densities is selected in a case other than the SA=0, the dot area ratio corresponding to the selected combination of color densities is determined by the dot area ratio interpolation means 60. Interpolation is performed to obtain a combination of dot area ratios that can print a color that is even closer to the color of the object to be measured.

First, from the color density-dot area ratio conversion table with dot area ratios in 10% intervals as shown in Figure 2, the color density combination d (D _R , _DG , D _B , D _A ) of the object to be measured is determined. The closest one is selected and its color density combination is t
(T _R , T _G , T _B , T _A ) and the corresponding combination of halftone area ratios is P (c, m, y, bk).

In the following explanation, to simplify the explanation, C, Bk is excluded as combinations of dot area ratios,
Although the explanation will be limited to the three colors M and Y, the interpolation process can be performed in exactly the same way even when Bk is not excluded.

FIG. 5 is an explanatory diagram of the interpolation method, and shows R, G, B
The axes represent the combination t (T _R , T G , T _B , T _A ) of color densities obtained through the R, _G , and B filters, respectively, as the origin.

Here, if the vector B→ _td (B _R , B _G , B _B ) is set, B _R =D _R −T _R , B _G =D _G −T _G , and B _B =D _B −T _B .

In addition, the dot area ratios are shifted by 1 unit (i.e., 10% in the case of FIG. 2) for each of the combinations P (c, m, y) of the dot area ratios corresponding to the color density combination t. combination P ₃ (c±10, m±10, y
±10) and the corresponding color density combination
t ₃ (T _R3 , T _G3 , T _B3 ) can be known from the color density-dot area ratio conversion table. The dot area ratio
Whether to take the positive or negative value of P ₃ (c±10, m±10, y±10) is determined by vector B → _td (B _R , B _G ,
It is determined depending on whether each component of B _B ) is greater than or equal to zero or less than zero, and if it is greater than or equal to zero, it is considered a positive value, and if it is less than zero, it is considered a negative value. In _{this case} , _c
The numbers to be adopted for each of ±10, m±10, and y±10 are determined.

Here, considering vector B→ _tt3 , vector B→ _tt3 can be expressed as a combination of several vectors.

Here, for the sake of simplicity, the following description will be made assuming that the vector B→ _td is a case in which each component is greater than zero, but the same process can be performed even in other cases.

The combinations of dot area ratios when the c component increases by 10% and when the c component and m component each increase by 10% with respect to the combination of dot area ratios P (c, m, y) are respectively P ₁ (c+10, m, y),
Let P ₂ (c+10, m+10, y).

The combinations of color densities corresponding to the combinations P ₁ and P ₂ of the dot area ratios are respectively t ₁ (T _R1 , T _G1 , T _B1 ) and t ₂ (T _R2 ,
T _G2 , T _B2 ).

Therefore, vector B→ _tt3 becomes vector B→ _tt1 , B→ _t1t2
,
By B→ _t2t3 , it can be expressed as B→ _tt1 +B→ _t1t2 +B→ _t2t3 =B→ _tt3 .

Therefore, vector B→ _td is vector B→ _tt1 , B→ _t1t2
,B→
_t2t3 is expressed as αB→ _tt1 +βB→ _t1t2 +γB→ _t2t3 =B→ _td .

Here, since each component of the vector B→ _td (B _R , B _G , B _B ) is known as described above, α, β, and γ are determined from the above relational expression.

Therefore, the color density combination d(D _R , D _G ,
The combination of halftone area ratios P( _c ,
A combination of dot area ratios P′(c′,
m', y') are at 10% intervals in the table in Figure 2, so c'=c+α×10 m'=m+β×10 y'=y+γ×10.

As described above, the combination of halftone area ratios after interpolation
P′(c′, m′, y′) is determined.

Note that there are various methods of expressing the vector B→ _tt3 as a composition of other vectors in addition to the above, and any vector may be used.

However, in order to obtain a reasonable interpolated value, the fifth
As shown in the figure, it is preferable to select vectors such that the vector obtained by connecting the combinations of color densities obtained from the color density-dot area ratio conversion table reaches the combination _t3 of color densities.

When the combination of color densities in the color density-dot area ratio conversion table and the combination of color densities of the object to be measured completely match, the dot area ratio display means 70 displays the matched color density combination. Corresponding combinations of dot area ratios are displayed, and if they do not match completely, a combination of dot area ratios interpolated as described above is displayed.

FIG. 6 is a flowchart showing how combinations of dot area ratios are determined using the apparatus according to the invention of this application described above.

Since the invention of this application has the above structure, it has the following effects.

First of all, as shown in FIG. 1, according to the apparatus of the invention of this application, even if the color to be reproduced in printing is specified as an actual color, such as in a color sample, even an inexperienced person can extremely easily reproduce the color. Moreover, in a short time, the halftone positive halftone dot area ratio of each color to reproduce the specified color can be determined.

Next, according to the device of the invention of this application, the halftone positive halftone dot area ratio of each plate is always determined in a standardized form, unlike the conventional method in which humans judge it, so the quality of printed matter can be controlled. becomes easier.

Further, according to the invention of this application, in addition to the above-mentioned effects, combinations of dot area ratios with even higher accuracy can be obtained very easily.

Further, according to the invention of this application, the processing time required for interpolation for determining the combination of highly accurate halftone area ratios is extremely shortened.

[Brief explanation of the drawing]

Fig. 1 is a conceptual diagram of the device of the present invention, Fig. 2 a, b
is an explanatory diagram of a color density-dot area ratio conversion table, FIG. 3 is an explanatory diagram of one embodiment of the color density measuring means, and FIG. 4 is a graph for explaining the relationship between color density and dot area ratio. FIG. 5 is a diagram for explaining a method for interpolating halftone dot area ratios, and FIG. 6 is a flowchart for determining a combination of halftone dot area ratios using the apparatus of the present invention. 1...Object to be measured, 10...First storage means, 2
0...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, 30... Second storage means, 40... Color density selection means, 70... Halftone area ratio display means, 60...
...Dot area ratio interpolation means.

Claims (1)

[Claims] 1. A first storage unit storing a color density-dot area ratio conversion table showing a correspondence relationship between a combination of color densities and a combination of dot area ratios corresponding to the combinations of color densities of a plurality of color separation plates. a storage means, a color density measurement means for determining the combination of color densities of the object to be measured, a second storage means for storing the combination of color densities determined by the color density measurement means, and the first storage. The combination of color densities in the color density-dot area ratio conversion table stored in the means is compared with the combination of color densities of the object to be measured stored in the second storage means to determine the color density-dot area ratio. color density selection means for selecting a combination of color densities closest to the color density combination of the object to be measured from among the combinations of color densities in the area ratio conversion table; If the combination does not match, the color density -
A dot area ratio interpolation means that calculates a combination of dot area ratios interpolated by a vector method based on a dot area ratio conversion table, and a combination of the selected color densities and the color densities of the object to be measured match. and a halftone dot area ratio display means for displaying the interpolated halftone dot area ratio when the color density combination is not selected, and displaying the combination of the halftone dot area ratio corresponding to the selected combination of color densities when they match. A dot area ratio determining device characterized by: