JPH1016198A - Gradation measuring apparatus for printed matter - Google Patents

Abstract

PROBLEM TO BE SOLVED: To calculate adjusting quantity easily and accurately by accurately detecting a gradation and to easily arrange the hues of a large quantity of printed matters by subjecting the measured values of the reflectivities of reference matter and objective matter to regression analysis corresponding to inks of the three primary colors to calculate corresponding coefficients and detecting the shift of the hue of objective printed matter on the basis of the difference between both coefficients. SOLUTION: The output of a rotary encoder 6 is inputted to a measuring control circuit 10 to output a measuring trigger signal to a spectral colorimeter 8 and solid angle reflectivity is measured from polynominal expression according to regression analysis by a regression operation circuit 12. The coefficient of the spectral waveform of each color is calculated and ink amt. is adjusted on the basis of the coefficient of regression and the coefficient of regression is stored in a color evaluation part 14 as a reference value. Next, the printed matter to be measured continuing to a reference sample is measured in the same way and the color evaluation part 14 adjusts the amt. of ink so that the difference of the coefficient of regression becomes zero and the corresponding relation of the coefficient of regression and the opening degree of the ink key is stored in a data base 16 and color shift quantity is displayed on a display part 20. Therefore, the difference of a gradation with proof and a hue change during printing can be judged and a hue can be a utomatically controlled.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a color tone measuring apparatus for measuring the color tone of a printed material on which the same picture is repeatedly printed, such as a printed material printed by an offset printing machine or the like.

[0002]

2. Description of the Related Art In a printing operation, the color tone of a proof print and a final print are adjusted at the start of printing, or a change in the characteristics of a printing press due to a change in temperature or humidity during printing, and a change in material properties (mainly ink). It is necessary to correct the color tone by the change. This work looks at the printed matter, accurately judges the difference in color tone from the reference printed matter, and adjusts the amount of ink called ink keys arranged in a large number in the width direction of the printing press (the direction orthogonal to the direction in which the printed matter flows). This is done by adjusting each of the mechanisms. In many cases, it is necessary to rely on the intuition of a skilled worker to accurately judge the difference in the color tone by looking at the printed matter to be measured. It is also possible to use a densitometer or a spectrophotometer to measure a part of the picture that is particularly important for color tone management, or a part called a control patch and printed for measurement separately from the picture. However, determining the amount of adjustment based on the measurement results also relied on the intuition of a skilled worker.

For this reason, in the conventional printing operation, a great deal of cost and time are required for securing skilled workers, maintaining and improving the skill level. Also, conventionally, since the printed matter that was cut and discharged from the folding machine was taken out and measured and evaluated, when color misregistration occurred, it took time to detect the color misregistration and adjust the ink amount, In the meantime, a large number of color defective prints will be printed.

[0004]

As described above, the conventional color tone measuring apparatus for a printed material cannot detect color misregistration quickly and cannot find an appropriate adjustment amount according to color misregistration. .

SUMMARY OF THE INVENTION The present invention has been made in view of the above-described circumstances, and has as its object to accurately measure the color tone deviation of a printed material, to easily obtain an accurate adjustment amount, and to adjust the color tone of a large number of printed materials. An object of the present invention is to provide a color tone measuring device for printed matter that can be easily aligned.

[0006]

According to the present invention, there is provided an apparatus for measuring the color tone of a printed material, comprising means for measuring the reflectance of a reference printed material and a printed material to be measured in a predetermined range; A means for obtaining a coefficient corresponding to the ink of the three primary colors by performing regression analysis using a polynomial including a known spectral waveform corresponding to the inks of the three primary colors, and corresponding to the inks of the three primary colors in the reference printed matter and the printed matter to be measured Means for detecting a shift in the color tone of the printed matter to be measured based on the difference between the coefficients to be measured. Here, the regression analysis means can also perform a regression analysis on the measured values of the measurement means using a known spectral waveform corresponding to the three primary color inks and a polynomial expression including the pattern area ratio of the three primary color inks of the print to be measured.

According to the apparatus for measuring the color tone of a printed matter according to the present invention, a value corresponding to the ink amounts of the three primary colors of indigo, red and yellow is obtained from one measured value by regression analysis. Since the color shift is detected, the color tone shift of the printed matter can be accurately measured, an accurate adjustment amount can be easily obtained, and the color tone of a large number of printed matters can be easily aligned.

[0008]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, a first embodiment of a color tone measuring device for printed matter according to the present invention will be described with reference to the drawings.
FIG. 1 is a block diagram showing the configuration of the first embodiment.
In the first embodiment, a color printer which is incorporated in a printing press, measures the color tone of a printed matter in real time, and detects a change in the color tone will be described. FIG. 2 is a perspective view showing the arrangement of the spectrophotometer.

As shown in FIG. 2, a spectral colorimeter 8 is provided on the traveling path of the printed matter 2 near the final stage of the printing press (for example, between the cooling unit and the folder in the case of an offset rotary press). The spectrocolorimeter 8 measures the solid angle reflectance of a predetermined point of each picture at a position separated from the printed matter 2 by a minute distance (for example, 1 mm or less, preferably about 0.2 mm). Therefore, in order to synchronize the position of the measurement point with the picture, a rotary encoder 6 for grasping the position of the flowing printed matter is attached to the transport roller 4, and the spectrophotometer 8 measures in synchronization with the output of the rotary encoder 6. . That is, the measurement is started and ended by the pulse signal from the rotary encoder 6. Since the printed matter is flowing, by performing measurement for a predetermined period, an integrated value of measured values in a predetermined range is obtained. As described above, the rotary encoder 6 is provided for accurately measuring a part of a picture, one picture, or several pictures.

Since the color tone of the printing press is adjusted by ink keys arranged in the axial direction of the inking roller (in the direction perpendicular to the direction in which the printed material flows), the spectral colorimeter 8 is set at a position corresponding to the position of the ink key. Preferably, there is.
That is, a large number of the spectrophotometers 8 are mounted at positions corresponding to the respective ink keys, or the colorimeters 8 can be moved in the axial direction so that the positions corresponding to the respective ink keys are sequentially set by one colorimeter 8. Be able to measure.

Returning to FIG. 1, the output of the rotary encoder 6 is input to the measurement control circuit 10, and the measurement control circuit 10 supplies a measurement trigger signal to the spectrophotometer 8. The output of the spectrophotometer 8 is supplied to a regression operation circuit 12, where a regression coefficient is obtained. The regression coefficient is supplied to the color evaluation unit 14, and the ink adjustment amount is obtained by referring to the data in the database 16. The obtained ink adjustment amount is supplied to the ink key 18 as a control signal, and is also supplied to the display unit 20 for display.

The operation of the first embodiment will be described. In general, in printing, a reference sample is printed before actual printing, and the color of the actual print to be measured is adjusted based on the reference sample. First, a reference sample is measured. Reference samples include customer-reviewed proofs, prints that are actually printed in the presence of the customer and approved by the customer,
Or there are printed materials etc. confirmed by a skilled inspector,
In the present invention, since the measurement points are controlled by the rotary encoder 6, printing actually starts and a printed matter confirmed by a skilled inspector is used. That is, when a desired color tone is obtained, a pulse is generated from the rotary encoder 6.
Since the picture is continuously printed on the printing paper at a predetermined interval, the measurement range can be specified by the output of the rotary encoder 6. The measurement control circuit 10 supplies a measurement trigger signal to the spectrophotometer 8 in response to a pulse signal corresponding to a predetermined position of the picture to measure the solid angle reflectance. The measured values are subjected to regression analysis in the regression operation circuit 12 using the following polynomial.

Yλmeasure = α · λc + β · λm + γ · λr + constant (1) Here, Yλmeasure is a measured value. Also, λc, λ
m and λr are spectral waveforms corresponding to the three primary colors of indigo, red and yellow ink, respectively, which are specially printed portions for color tone measurement called control patches printed on a reference print. (A small printing range of each of indigo, red, and yellow) or data measured in advance at another occasion. Spectral waveform data λc, λm, λ
r is stored in the database 16.

By the regression analysis, coefficients (hereinafter, referred to as regression coefficients) α, β, and γ for the spectral waveform of each color are obtained. Since the regression coefficient corresponds to the ink amount, in the present invention, the color shift is detected based on the regression coefficient, not the measured value of the spectral colorimeter 8, and the ink amount is adjusted based on this. The regression coefficients α, β, and γ obtained from the measured values of the reference samples are supplied to the color evaluation unit 14 and stored as reference values.

Next, the solid angle reflectance of the corresponding point is also measured on the printed matter to be measured following the reference sample. That is, when the pulse signal from the rotary encoder 6 becomes a signal corresponding to the position of the measurement point of the reference sample, the measurement control circuit 10 supplies a measurement trigger signal to the spectrophotometer 8 to measure the solid angle reflectance. The measured value is subjected to regression analysis in the regression operation circuit 12 by the following polynomial in the same manner as in the case of the reference sample.

Yλmeasure '= α'.lambda.c + .beta.'. Lambda.m + .gamma. '. Lambda.r + constant (2) The color evaluation unit 14 calculates the difference (corresponding to the amount of color misregistration) of the regression coefficients α-α', β-β ', γ- The ink amount is adjusted so that γ ′ becomes 0. Regression coefficient differences α-α ', β-β',
The correspondence between γ-γ ′ and the ink key opening is checked in advance, and stored in the database 16 as a table. Therefore, when the difference between the regression coefficients is determined, the ink adjustment amount is specifically determined as a numerical value. The display unit 20 displays the amount of color shift based on the difference between the regression coefficients.

As described above, according to the present embodiment, a value corresponding to the ink amounts of the three primary colors of indigo, red, and yellow is obtained by regression analysis from one measurement value, and the value is determined in accordance with this variation. Since the color misregistration of the printed matter is detected, the color tone misregistration of the printed matter can be accurately measured, an accurate adjustment amount can be easily obtained, and the color tone of a large number of printed matters can be easily adjusted.

The present invention is not limited to the embodiment described above,
Various modifications are possible. For example, the following polynomial may be used as the regression equation. Yλmeasure = αi · Ac · λc + βi · Am · λm + γi · Ar · λr + constant (3) where Ac, Am and Ar are the indigo of the measurement part,
The pattern area ratio of the red and yellow inks is measured at the time of plate making and stored in the database 16.

According to the equation (3), the picture area ratio can be considered, and it is considered that the accuracy is higher than that of the equation (1).
In the above-described embodiment, the case where the printed matter is incorporated in the printing machine has been described.However, when measuring a printed matter sampled after printing, the printed matter is fixed on a table, and the colorimeter is moved at a constant speed on the printed matter. I just need. Further, both the printed matter and the colorimeter may be moved. In this way, the proof can be used as a reference sample.

[0020]

As described above, according to the present invention, it is possible to judge a difference in color tone between a proof print and a printed matter, or a change in color tone during printing, without relying on the intuition of a skilled worker, by a rational method. it can. In addition, since the difference in color tone can be obtained as an increase or decrease in the amount of ink for each color, the amount of work for the color matching operation (ink key operation) can be estimated, and automatic control of the color tone by adjusting the amount of ink can be realized. Further, since the printed matter can be directly measured on the printing press, the operation for evaluating the color tone from the evaluation of the printed matter becomes faster, leading to a reduction in printing defects.

[Brief description of the drawings]

FIG. 1 is a block diagram showing a configuration of a first embodiment of a color tone measuring device for printed matter according to the present invention.

FIG. 2 is a perspective view showing the arrangement of the spectrophotometer in the first embodiment.

[Explanation of symbols]

2 Printed matter 4 Transport roller 6 Rotary encoder 8 Spectrocolorimeter 10 Measurement control circuit 12 Regression operation circuit 14 Color evaluation unit 16 Database 18
... Ink key, 20 ... Display part.

 ──────────────────────────────────────────────────続 き Continuation of the front page (72) Inventor Tatsuya Kakiuchi 1-5-1, Taito, Taito-ku, Tokyo Letterpress Printing Co., Ltd.

Claims (2)

[Claims] 1. A means for measuring reflectance in a predetermined range of a reference printed matter and a printed matter to be measured, and a measured value of the measuring means includes a known spectral waveform corresponding to three primary colors of printing ink. Regression analysis means for performing regression analysis using a polynomial to obtain coefficients corresponding to the three primary color inks;
Means for detecting a shift in the color tone of the printed material to be measured based on the difference in the coefficients corresponding to the primary color inks. 2. The regression analysis means performs a regression analysis of the measured value of the measurement means by a polynomial including a known spectral waveform corresponding to the three primary color inks and a pattern area ratio of the three primary color inks of a print to be measured. The color tone measuring device for printed matter according to claim 1, wherein: