JPS5994759A - Deciding device for area rate of dot - Google Patents

Abstract

PURPOSE:To combine easily dot area rates of respective color plates by finding a dot area rate closest to the color density combination of a body to be measured in a color density dot area rate conversion table which is stored previously and displaying a combination of dot area rates. CONSTITUTION:The 1st storage means 10 stores the color density-dot area rate conversion table previously. Combination data on the color density of the body to be measured is found by a color density measuring means 20 and stored in the 2nd storage means 30 temporarily. Both stored data are compared with each other by a color density selecting means 40 to select a dot area rate closest to the combination of color density of the body to be measured and the combination of the dot area rate corresponding to said color density combination in said conversion table is displayed on a display means 50. Consequently, combinations of dot area rates of respective color plates of Y, M, C, and BK are determined easily for any color.

Description

Detailed Description of the Invention This invention +S, C (cyan), M (magenta) for printing from the density value measured through a filter on the object to be measured
, Y (yellow), and Bk (plaque).

Conventionally, printing layout sheets sometimes include a large number of color samples for specifying colors.For example, when you want to uniformly fill a background with a certain color, you can use a small A piece of paper is attached as a color sample.

If you want to print the specified part with the same color as this color sample C
, M, Y, Bl (To determine what halftone area ratio to print each plate, use this color sample and a color chart with the halftone area ratio changed at approximately 10% intervals. visually compare and select the most similar one,
The selected color is generally determined based on the fact that the percentage of the halftone dot area of each plate is written on 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 Niel-Nielsen equation is usually used to calculate the dot area ratio from this density value. In order to use this Niel-Nielsen equation, first measure the reference density, set the halftone area ratio of that part to the reference value (100%), and then measure the actual halftone area. It is necessary to measure the object to be measured and use the relationship with the reference concentration.

Therefore, it is only applicable to colors that have a standard density, and is usually used only for monochrome colors. Moreover, the Niel-Nielsen equation can be established by ideally reproducing halftone dots without dots, 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 when using a single color. Moreover, it is difficult to calculate the halftone area ratio of secondary colors or higher.

Therefore, such a densitometer cannot display a combination of halftone area ratios for each of the Y, M, C, and Bk versions to express the color of the color sample.

In addition, such a conventionally known densitometer has the following reasons:
M, c: It is impossible to display the combination for each version of Bk (that is, printing ink Y, M,
The 1st ink of C is not ideal (in the Y ink &
j The M ink contains the M component and the C component, the M ink contains the Y component and the C component, and the C/I ink contains the M component and the Y component. Y used in reality
Because the printing inks of IM and C are not ideal,
Neal the density value obtained by measuring the color of the object to be measured, such as a color sample, through filters B' (blue violet), G (green), and R (red), which are complementary colors of YlM and C. - Even if the dot area ratio is calculated using Nielsen's formula, the value does not indicate the actually required dot area ratio for each positive chip of Y, M, and C. 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 dot area ratio of ioo% is printed using only C ink from a certain ink manufacturer. If you calculate the density of this printed matter through an R filter, a G filter, and a B filter, each will be 1.56.0.
52.0.17, but these values are respectively R and ()
, B, it is clear that it cannot be used to determine the halftone area ratio of the c, M, and y versions.

This problem is not limited to just one color of ink (it becomes even more complicated when multiple colors of ink are to be overprinted).

The present invention eliminates the above-mentioned various drawbacks, and allows any color to be printed with YlM, C color ink or &X
It is an object of the present invention to provide an apparatus that can easily determine how to combine the halftone area ratios of each color plate when expressing with ink of each color of Y, M, C, and Bk.

That is, the first invention of this application is a color density-dot area ratio conversion that shows the correspondence between a combination of colors and a combination of dot area ratios corresponding to the combination of color densities of color separation plates of multiple colors. a first storage means in which a table is stored; 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 measurement means. storage means, the color sensitivity-dot area ratio conversion table combination stored in the first storage means, and the color 4 of the object to be measured stored in the second storage means;
color density selection means for selecting the color density combination closest to the color density combination of the object from among the color density combinations in the color specularity-X point area ratio conversion table; An object of the present invention is to provide a halftone area ratio determination device comprising a halftone area ratio display means for displaying a combination of halftone area ratios corresponding to a combination of color densities selected by a color selection means. It is.

Furthermore, a second invention of this application provides an apparatus that can obtain more detailed combinations of dot area ratios using a table similar to the chromaticity-dot area ratio conversion table used in the first invention. This is what we are trying to provide.

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 the first invention of this application,
The first storage means (10) is stored in advance in a color density-dot area that indicates a correspondence relationship between a combination of color densities and a combination of halftone dot area ratios corresponding to the one-time combination of colors of a plurality of color separation plates. The point area ratio conversion table 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 object to be measured is stored in the second storage means (30). Once it is memorized. As the color combination data stored in the second storage means (30), for example, the color sensitivity of the object to be measured is determined by six types of data obtained through each of the R filter, G filter, and B filter. One set of color combinations, and one set of four types of color sensitivities, in which color density obtained through an amber filter or ND filter is added to each of the above-mentioned filters. It is something. Next, color density selection means (40)
+! , a combination of the color densities of the color density-dot area ratio conversion table stored in the first storage means aO) and a combination of the color densities of the object to be measured stored in the second storage means (30). A combination of color densities closest to that of the object to be measured is selected from among the combinations of color densities in the color basis-dot area f 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 color combination of the object to be measured is determined by the dot area ratio display means ( 50). 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.

Figure 2 (8), (llll shows an example of a color density-halftone area ratio change table, and the left side shows the data obtained through each of the R filter, G filter, B filter, and amber filter. The combinations of color densities shown on the right side are shown, and the combinations of halftone area ratios corresponding to the color density combinations shown on the left side 1 are shown on the right side.

Such a color density-dot area ratio conversion table is created as follows. First, print Y and M on the printing paper.

Using each of C and Bk inks, the halftone area ratio is 0% to 1.
00% at appropriate intervals, for example, as in the case of Figure 2 (10% interval), and actually print and create a color chart. In other words, in the example of Figure 2, number 1
~ No. 11 has a halftone area ratio of 0% for M, Y, and Bk versions.
Only the C plate is changed from 0% to 100% in 10% increments, and the dot area ratio of the Y and Bk plates is 0%, and the dot area ratio of the M plate is 10%. %, and only the C version is changed by 10% between 10% and 100%.
Below, the halftone area ratio of each version of Y, M, and C1Bk is set to 1.
Color charts were created using various combinations that were changed at υ% intervals. Such a combination &XY, M, C.

't' when the halftone area ratio is changed at 1υ% intervals for each version of Bk! 11'=14641 combinations are generated.

Combinations of color sharpness obtained through the R filter, G filter, B filter, etc. for each color of the color chart created as described above, or in addition to this, an amber filter or ND filter. Find the combination of colors obtained through the filter by adding one color.Thus, for various colors, we can find the correspondence between the combination of color density and the corresponding combination of halftone area ratio of each color plate. A color density-dot area ratio conversion table is created.

In addition, the above R, (), B, Ambermata & jND
It is common to measure color density using each of the following filters, but an interference filter or the like having a peak in the absorption portion of the spectral reflection curve of printing ink may also be used. The same filter used to create the color hardness-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, in numbers 1 to 11 in FIG.
C even though it doesn't change at 0 and only the C version changes
(
, the color density through the other G, B, and Amber filters is also changing.

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 the object to be measured, it is necessary to take into consideration 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 00), and an appropriate storage means such as a magnetic disk, a floppy disk, or a Rotφ is used as such storage means.

As described above, the colors -
A halftone dot area ratio conversion table is stored.

Color density measurement again? The 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 to be measured (1) such as a color sample is irradiated by a light source (2υ), and the reflected light is sent to a photoelectric conversion element (23) via a filter (2υ).
where it is converted into an electrical signal.

The filter (22) is the same as that used when creating the color saturation-dot area ratio conversion table, and is R
Six types of filters, G filter, and B filter, or four types of filters, including an amber filter and a 'ts ND filter, are installed in a convertible manner. In this case, the filter may be switched electrically or manually. Furthermore, in the example shown in Fig. 6, the light from the light source is emitted from an angle of 45 degrees and is received directly above, but the light is emitted from directly above and received at an angle of 45 degrees.
The light may be received in a direction of 5 degrees. The electrical signal generated by the photoelectric conversion element (23) is amplified by the amplifier circle, subjected to necessary correction by the correction circuit (29), and then sent to the logarithmic converter (26).
) is subjected to logarithmic conversion processing, and then converted to an A/D converter (27
), the analog signal is converted into a digital signal, and the color density is input to and stored in the second storage means (3o).

Note that the value of the electrical signal that has been logarithmically converted by the logarithmic converter (26) can be checked on a display meter 128). Note that the display meter (2υIts) may be placed after the A/D converter (27) to provide a digital display.

As described above, by measuring the object to be measured for each filter, combinations of color densities of the object to be measured are obtained, and these are determined as described above (
The data is stored in the second storage means (3o). As the second storage means (30), an appropriate one such as RAM can be selected.

Color density selection means (40) &! Second storage means (30)
The combination of color densities of the object to be measured stored in is compared with the combination of color densities in the color density-dot area ratio conversion table stored in the first storage means (10), and the color density-dot area is calculated. Among the combinations of color densities in the rate conversion table, the one closest to the combination of color densities of the object to be measured is selected as follows.The R filter of the object to be measured, The color density obtained through each of the G filter, B filter, and amber filter is DR and DG.
N DB N DA, and the color densities through the R filter, G filter, B filter, and amber filter at the nth number of the color density-dot image output conversion table are respectively TR(n) and TG( n),
Let TB(n) and TA(n). Next, the combinations DR, DG, DB, DA of the color densities of the object to be measured and the n-th number combinations TR(n), TG(n) of the color densities in the color density-dot area ratio conversion table. , TB(nl, TA(
A combination of color densities TR(n), To(n), TB(n), T that minimizes the distance S A(n) between
Find A(n).

Distance Sban) is C3A&):]2=(:TR(n) DR:]2+(
To(n)-DGI2+ [TBfn) DB) 2
+ [TA(n) DAI It is determined from the relational expression 2.

The value of n that minimizes the distance s A(g))j (SA(n
)] 2 matches the minimum value of n. Therefore, using the above relational expression, find the combination of color densities in the color density-dot area ratio conversion table that minimizes [5A(n)]2.
= By searching sequentially by changing the value of n from i to the end, we can find the value of n that minimizes 5A(n).

Determine the combination of color densities in the color density-dot area ratio conversion table corresponding to n that minimizes S A(n) as the one closest to the combination of color densities of the object to be measured, and select that combination of color densities. The combinations of dot area ratios of the y, M, c, and Bk versions corresponding to the image are determined.

In this case as well, if [5A(nl)2 becomes zero during the search, in other words, during the search, the combination of the color densities of the object to be measured and the color density in the color density-dot area ratio conversion table If a match is found, the combination of halftone area ratios corresponding to the combination of color densities at the value of n at that time is the desired data, and the subsequent search may be discontinued.

The combination of the halftone dot area ratios of the Y, M, C, and Bk versions determined as described above is displayed in the halftone dot area ratio display means (50).
Displayed by As the dot area ratio display means, an appropriate device such as a printer or a CRT display can be used.

The combination of halftone dot area ratios displayed as described above indicates the halftone dot area ratio of each plate, and if printed using each color ink based on the combination of halftone dot area ratios obtained in this way, the measurement result will be It is possible to obtain a printed matter that is the same or similar to the color of the object.For example, if the 125th color density is selected as the closest color density to the combination of color densities obtained by measuring the object, the second From the table in the figure, the 0 version is 60% and the M version is 0.
%, Y version is displayed as 10%, and Bk version is displayed as 0% by the dot area ratio display means. Therefore, by printing using ink of each color in the combinations 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, the solid performance value used as the standard when creating the data for the color density-dot area ratio conversion table may differ from the solid density value used as the standard at the printing factory when actually printing. In some cases, it may be. In such cases, the conditions for creating the color vagueness-dot area ratio conversion table and the conditions for actual printing are different, so the colors in the color density-dot area ratio conversion table are different. When comparing the combination of densities and the combination of color densities of the object 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, The case where the stripe is approximately corrected is shown.

Figure 4 is a graph for explaining the relationship between color density and halftone dot area ratio.For simplicity, the explanation will be based on the assumption that they have a linear relationship, but the same concept can be applied to curved lines. Then, the correction can be made.

In Figure 4, when creating the color density-dot area ratio conversion table, the part where only the 0th edition is 100% and all other editions are 0% is changed to the color obtained through the R filter, which is the complementary color of C. Assume that the density is Xc, and all the plates are 0%, that is, all the ink is on the color chart paper (the color density obtained through the R filter in the unapplied area is N). Solid printing is performed in advance on six sheets of paper using a 0 plate with a density determined as the standard solid density at the printing factory and a plate with a halftone area ratio of 100%. The color and 6 degrees measured by the device of the present invention through the R filter are the solid density of the 0 plate printed on the paper to be printed. Assume that the color density obtained by measuring [-] using the R filter is N.'. In Fig. 4, the straight line (a) and the straight line (b) represent the color density -
It shows the relationship between color density and dot area ratio when creating a dot area ratio conversion table and when actually printing. In this case, the color density of the object to be measured, such as a color sample, is obtained by passing it through an R filter using an inventive device. ', then if the dot area ratio is calculated without any correction, the dot area ratio P' will be obtained, but a value different from the dot area ratio P that should be actually obtained will be obtained. I end up. Therefore, the color density obtained by measuring the error in this case is -. When the color density after correcting the value of ' is set to DC, xC-N, )D. = (D.'-N,') X--7+N.

xc-N.

The color density of the object to be measured obtained through the R filter is corrected according to the relational expression. Similarly, only the M version is 100%,
For the Y version printed at 100% and the Bk version printed at 100%, the color density is determined through the G filter, B filter, and amber filter, respectively.
Furthermore, the color density of the paper itself is determined through the G filter, B filter, and amber filter. Using these color density data, the measured object is filtered through the G filter, B filter, and amber filter (also & XND filter). )
The color densities obtained through the process are also corrected, and the respective corrected output color densities are combined. , Do, DB, and DA are used for comparison with color density combinations in the color density-dot area ratio conversion table. 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 color densities of the reference solid printed area of each color ink at the printing factory were measured using the apparatus of the present invention through an R filter for C ink, a G filter for M ink, a B filter for Y ink, and an amber filter for European ink. These data were stored in the device of the present invention.Next, the object to be measured was measured using the device of the present invention through R, (), B, and 7-bar filters. The color density is corrected using the previously determined color density of the paper and the color density value of the reference solid print area.

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

Furthermore, another method of correction is as follows when a kill densitometer is used as a color density measurement means by adjusting the light part and shadow part independently for each R, G, B, and amber filter. You may.

That is, the light unit measures the unprinted portion of the paper to be printed, and each of C, M, Y, and Bk in the color density-dot area ratio conversion table is 0% (
R, (in the case of number 1 in Figure 2) so that the color density is
), B, and amber filters, and the shadow area is adjusted using the paper c, M, y, and paper to be printed.
Prepare a print with a standard solid density for each Bk color ink, measure the solid density part of the C ink through an R filter, and calculate the color density of the shadow part at this time by calculating the color density - Adjust the color density of the R filter when C in the halftone area ratio conversion table is 100% (for the number 11 band in Figure 2), and similarly adjust the color density of M ink, Y ink, and Bk ink. Regarding "G filter, B filter, and anonymous filter, when each of Y, M, and Bk in the color density-dot area ratio conversion table is 100%, G filter, B filter, and amber are measured through G filter, B filter, and anonymous filter. Adjust to match the color density of the filter.

After making these adjustments, the actual object to be measured is measured to determine the combination of dot area ratios.

Various correction methods have been explained above, but all of them are 10
Only 0% correction is possible.

FIG. 5 is a flowchart showing how combinations of dot area ratios are determined using the apparatus of the present invention, including such corrections.

In Fig. 5, the number of the color density-dot area ratio conversion table when the distance is the minimum value is memorized, and the dot area ratio is calculated from this number. , instead of storing the dot area ratio data of each plate, only the data of the color density combinations can be stored in a predetermined order (because it only requires a small storage capacity) This is convenient because a storage means can be used.

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

Therefore, if you need a more accurate halftone area ratio, you can create a color density - halftone area ratio conversion table with the required accuracy. The amount of data in the area ratio conversion table is extremely large, and creating such data is extremely time-consuming and requires a storage device with a large storage capacity. The drawback is that it takes a long time to perform comparison operations with data.

The second invention of this application eliminates such drawbacks and provides a method for determining the halftone area ratio at intervals finer than the data interval of the halftone area ratio in color density-halftone area ratio conversion tape summarization. The aim is to provide a device that can.

That is, the second invention of this application is a combination of color densities and a combination 5 of the color densities of color separation plates of a plurality of colors.

Color density indicating the correspondence relationship between the halftone area ratio combination corresponding to the first storage means storing the halftone area ratio conversion table; and color density measurement for determining the combination of color densities of the object to be measured. and a combination of color densities determined by the color density measuring means (the second storage means and the first 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 - 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 halftone area ratio conversion table; and the combination of the selected color densities and the color of the object to be measured a dot area ratio interpolation means for determining a combination of interpolated dot area ratios based on the color density-dot area ratio conversion table when the combinations of densities do not match; and a combination of the selected color densities; If the combinations of color densities of the object to be measured do not match, display the interpolated dot area ratio; if they match, display the combination of dot area ratios corresponding to the selected combination of color densities. and halftone dot area ratio display means.

FIG. 6 is a conceptual diagram of the device of the second invention of this application,
The first one stores the color density-dot area ratio conversion table.
The storage means GO+, the color density selection means 4, the second storage means (30), and the color density selection means (40) are the same as those in the first invention, and the colors closest to those in the first invention are The combination of densities is selected from the 2 color densities - 7 halftone dots and 2 rate conversion tables.

The combination of color densities selected in this way is the distance SA
= O, that is, if it is selected as a result that perfectly matches the combination of color densities of the object to be measured,
Then, the corresponding combination of dot area ratios may be displayed as is on the dot area ratio display means (70). However, if the selected combination of color densities is selected in a case other than 5A=0, the dot area ratio corresponding to the selected color density combination is calculated by the dot area ratio interpolation means ( Interpolation is carried out at (hu) 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.

How to interpolate the dot area ratio will be explained below.

First, select the color density combination d (island, Do, DB, DA) of the object to be measured from the color density-dot area ratio conversion table with dot area ratios in 10% intervals as shown in Figure 2. is selected, and the combination of color densities is t(TR1To, TB, T
c) and the corresponding combination of halftone area ratios P(c,
m, y, bk). In this case, for example, the dot area ratio is 1
Assume that we want to obtain even the order of %. In this case, the fixed point area ratio to be determined exists within the dot area ratio shifted by half of 10%, that is, 5%, in the direction of magnitude with P as the center. In the following explanation, in order to simplify the explanation, we will limit the halftone area ratio power combination to six colors, C, M%Y, excluding Bk, but all (similarly This allows interpolation processing to be performed.

Figure 7 shows points C, M, which represent the dot area ratio, with the dot area ratio shifted by 5% in the direction of size with P as the center.
A expressed in the Y coordinate system (c+5, m-5, y+5
), B(c+5, m + '5, y+5), C(c+5
, m+5, y-5), D(c+5, m-5, y-5),
E(c-5, m-5, y+5), F(c-5, m+5
, y+5), G(c-5, m+5, y-5), H(c-
5, m-5, y-5), and the desired dot area ratio exists in a solid having these points as vertices.

Therefore, this solid is divided into parts with the required precision as shown in Figure 7, and the combination of color densities is determined for each combination of halftone area ratios shown by each grid point. It is sufficient to select a point at which the value is the minimum and determine the combination of dot area ratios at that point as a combination of dot area ratios with increased accuracy.

However, the dot area ratios of the points A, B, C, D, E, F, I) and H are known as described above, but the corresponding color densities are unknown.

Therefore, A'(c+10. m
-10, Y+10), B'(c-No, m+10, y+
10), C'(c+10, m+10, y-10>, D
'(c+10, m-10, y-io), E'(c-10
, m-10, y+10), F'(c-10%m-1-
10,y+10), o'(c-=-16,m+10,y
-1o), H'(c-10, m-10, y-10)
and their respective midpoints I (c, m-10, y+10),
J (c, m+10, y+1 o ), K (c, m+
10, Y-10), L (c, m-10, y-io), M
(c+1 o, m, Y+10), N(c+10, m
+10, y), O(c+10, m%M=10), Q (
c+10. m-10, y), R(c, m, y+1
0), S(c, m+10, y), T(c, m%y-
10), U (c, m-10゜y), V (c-10, m,
y+10), W(c-10%m+10.7), X(
c-10, m, y=10), Y (c=10. m
-10,y), Z(c+10,m,y),zz(c-
Since the combination of color densities of 1o, m, y) can be known from the color density-dot area ratio conversion table, first, using the color density values of each of these points and the color density value of point P, The combination of color densities of points A, B, C1D, E, F, G, and H is determined by interpolation calculation.

FIG. 8 shows the position of each point 10% away from point P in the C, M, Y coordinate system representing the halftone area ratio.

First, a method for finding a combination of color densities at point A (c+5, m-5, y+5) using an interpolation method will be described. Point A is shown in Figure 8 as point A'(c+10. mu, 'y+1
0), M(c-zo, m, y+10), Z(C+
10% m, y), Q(c+10, m-10, y), ■(
c, m-10, y+10), R(c, m.

y-H'o), p(c, m, y), U(c, m-10
%y). Therefore, the average of each color density component of points ACM, Z, Q, ■, R, P, and U is determined, and the value is taken as the color graininess component of point A, that is, the combination of the color density of point A.

Note that if the color density-dot area ratio conversion table is not created using equally spaced dot area ratios, points A', M, and Z
, Q, I, R, P, and U may be a rectangular parallelepiped rather than a cube, and in that case, the distance of point A from each vertex of the rectangular parallelepiped will be different, so from each vertex It may be determined using a proportional calculation formula or an appropriate function depending on the distance between.

Similarly, other points B, C, D%E, F, 0. A combination of color densities for each of H is also calculated.

As described above, we have found the combination of color densities for all points A, B, C, D, E, F, and G. Next, we will use the color densities of these points to calculate the Combinations of color densities at grid points obtained by dividing a cube as shown in FIG. 7 at necessary intervals are obtained using an appropriate method such as proportional allocation in the same manner as described above.

Next, the combination of the color densities of each grid point obtained in this way and the color densities of the object to be measured d' (DRs DG%
DB) is selected such that the distance SA is the minimum. At the grid points selected in this way, the combination of the dot area ratios is already known, so the combination of the dot area ratios is the combination of the dot area ratios of the object to be measured P (c
, m, y) is input to the dot area ratio display means (screen) and displayed.

As the dot area ratio display means, an appropriate device such as a CRT display or a printer is used.

By the way, points A, B, c, D, E, as shown in FIG.
Obtaining the combination of color densities at all the grid points with the required precision for the entire area in F, G, and H requires a large number of grid points, making the processing difficult. Therefore, in FIG. 7, consider eight small solid bodies whose diagonals are lines connecting the point P and each vertex. In this way, the desired combination of color densities will be included in one of these small solids. Where it is included is determined by the color density combination d(DRlDo, DB) of the object to be measured.
is determined and determined based on which point is closest to the combination of color densities of vertices A to H.

Once a small solid is determined in this way, only for this small solid, the combination of color density 0 of each grid point separated by the required precision is determined by interpolation, and then the combination of color density of each grid point in this small solid is determined by interpolation. Combination d (D
The grid point closest to Rs Do , DB ) may be selected. In this way, the calculation time can be reduced to about one-eighth.

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 β4-point area ratio display means (7o) displays the matched color density. A combination of dot area ratios corresponding to the combination is displayed, and if they do not match completely, a combination of dot area ratios interpolated as described above is displayed.

Note that the required halftone area ratio may be entered using a numeric keypad or the like.

Figure 9 shows how the dot area ratios are combined using the apparatus in the second invention of this application described above.
FIG.

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

First of all, according to the device of the invention of this application, even if a color is specified such as a color sample (the color to be reproduced in printing is actually The positive halftone dot area ratio of each color that reproduces the specified color can be easily and quickly determined.

Next, according to the device of the invention of this application, the halftone dot area ratio of the halftone positive chip of each plate is always determined in a standardized form, unlike the conventional method in which it is judged by humans, so that the quality of printed matter can be improved. Easier to manage.

Furthermore, according to the second invention of this application, in addition to the above-mentioned effects, it is extremely easy to obtain a dot area ratio with the required accuracy.

[Brief explanation of the drawing]

Figure 1 is a conceptual diagram of the device of the first invention, Figures 2 (a) and b
) is an explanatory diagram of a color density-dot area ratio conversion table, Figure 6 is an explanatory diagram of one embodiment of the color density measuring means, and Figure 4 is a graph for explaining the relationship between color density and dot area ratio. , FIG. 5 is a flowchart for determining a combination of dot area ratios using the device of the invention shown in FIG. 1, FIG. 6 is a conceptual diagram of the device of the second invention, and FIGS. 7 and 8 are FIG. 9 is a diagram for explaining a method of interpolation processing of halftone dot area ratios in the second invention, and a flowchart for determining a combination of halftone dot area ratios using the apparatus of the second invention. (1)...Object to be measured (10)...First storage means (20)...Color density measuring means CD...Light source (
22)... Filter (23)... Photoelectric conversion element CI + Bleeding... Amplifier (25)... Correction circuit (
26)... Logarithmic converter (27)... A/D converter (c)... Display meter (30)... Second storage means (40)... Color density selection means (50
), (70)...Dot area ratio display means (60)...
・Dot area ratio interpolation means Patent applicant: Toppan Printing Co., Ltd. Representative Kazue Suzuki Figure 1 Figure 3 Figure 4 Figure 6 Figure 7 C

Claims (2)

[Claims] (1) A color density-dot area ratio variation table showing the correspondence between the combination of color and density and the combination of dot area ratios corresponding to the combinations of color densities of color separation plates of multiple colors is stored. a first storage means for storing 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; The combination of color densities in the color density-foot point area ratio conversion table stored in the first storage means and the combination of color densities are recorded in the second storage means! A color that is the closest to the color density combination of the object to be measured from among the color density combinations in the color density-dot area ratio conversion table by comparing the color density combination of the object to be measured with the desired color density combination of the object to be measured. This corresponds to a combination of density selection means and color density selected by the color density selection means. (A dot area ratio determining device comprising: a dot area ratio display means for displaying a combination of four-point area ratios. (2) A table storing a color density-dot area ratio conversion table showing a 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. 1 storage means, 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 combination of color densities determined by the color density measurement means; The combination of color densities in the color density-dot area ratio conversion table stored in the storage means of ゛t and the combination of color densities of the object to be measured stored in the second storage means are compared to determine the color. 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 density-dot area ratio conversion table; and the combination of the selected color densities and the object to be measured. dot area ratio interpolation means for determining a combination of interpolated dot area ratios based on the color density-dot area ratio conversion table when the combinations of color densities do not match; If the combination of color densities of the object to be measured does not match, the interpolated dot area ratio is displayed; if they match, the combination of dot area ratios corresponding to the selected combination of color densities. 1. A dot area ratio determining device comprising: a dot area ratio display means for displaying a dot area ratio.