JP2563167B2 - Print density correction method - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a method for correcting the print density of a printing surface by a printing machine.

[Conventional technology]

The printing density of the printing surface changes depending on the ink supply amount and dampening water supply amount to the printing plate surface.
The supply amount of dampening water is adjusted according to the number of revolutions of the ink feed roller of the ink fountain and the opening amount of the blade opposed to this and divided in the axial direction of the roller to the same roller. It is adjusted according to the number of rotations, and in the case of multicolor printing, these are provided for each printing unit provided for each color, and these are variable elements of the print density.

Therefore, for the purpose of controlling these print density variable elements and making the print density the optimum reference density, the print density of the printing surface extracted during printing is measured photoelectrically, and the reference density D _s and the actual density are measured. The correction value C is obtained from the difference (D _s −D) from D, and each print density variable element is controlled according to the obtained correction value C,
Recently, a method of correcting print density has been used.

However, as the coefficient used when determining the correction value, the coefficient obtained experimentally is almost fixed.

[Problems to be solved by the invention]

However, the actual printing conditions vary variously depending on the temperature, humidity, type of printing machine, printing paper, ink quality, etc., and in particular, there are long-term fluctuations due to seasonal changes.
Appropriate correction cannot be made only by the coefficient obtained experimentally, and the correction control is not stable immediately due to excessive or small correction situation, and a large amount of defective printing occurs during this period, resulting in an uneconomical problem. ing.

[Means for solving problems]

In order to solve the above-mentioned problem, the present invention is constituted by the following means.

That is, the print density of the printing surface is measured, the correction value C is obtained from the difference (D _s −D) between the reference density D _s and the actually measured density D, and the ink supply amount of the printing machine is calculated according to the obtained correction value C. In the method of controlling and correcting the print density, the difference A = (D _s −D _i-1 ) between the reference density D _s and the previously measured density D _i-1 is measured by the previous measurement with the current measured density D _i. Difference from density D _i-1 B = (D _i −
D _i-1 ) to obtain the ratio α = A / B, and the difference E _i = (D _s −D _i ) between the reference concentration D _s and the actually measured concentration D _i at this time and the corrected value at this time from the ratio α. C _i is obtained, and the ink supply amount is controlled according to the obtained correction value C _i .

[Action]

Therefore, the correction value is corrected by the ratio according to the latest printing condition, the correction situation is not excessive or insufficient, and the correction control becomes stable immediately.

〔Example〕

Hereinafter, the details of the present invention will be described with reference to the drawings illustrating examples.

FIG. 2 is a block diagram showing the structure, in which the reference paper 1 in the reference printing state is photoelectrically measured by a densitometer (hereinafter, DM) 2 and a color patch printed on the upper margin of the reference paper 1 and the like. The standard print density for each color is calculated based on the square print surface for each color, and the sample paper 3 extracted during printing is also measured by DM2 in the same way, and the current print density is calculated for each color. ing.

On the other hand, a control circuit that receives the output of DM2 (hereafter CNT)
4 is a processor such as a microprocessor (hereinafter, CP
U) 41, fixed memory (hereinafter ROM) and variable memory (hereinafter RAM) memory (hereinafter MEM) 42,
It is composed of interfaces (hereinafter I / F) 43 and 44, an input / output device (hereinafter referred to as IOE) 45 consisting of a keyboard and a display, and CPU 41 executes the instructions stored in the ROM of MEM 42 and is required. The control operation is performed while accessing the RAM of MEM42, and the control judgment result is obtained according to the setting data from IOE45 and the measurement output of DM2 via I / F43. It is sent to the printing press 5 via F44 to control the print density variable element for each color.

FIG. 1 is a diagram showing the correction status of the print density D by the above-mentioned control. The actually measured densities D _i-1 and D _i of the sample paper 3 with respect to the reference density D _s are the number of times m of extraction and measurement by DM2. And the correction status is insufficient, and the difference between the reference concentration D _s and the previously measured concentration D _i-1 is A = (D _s −D _i-1 ). The difference between the measured density D _{i of} this time obtained after correction based on this and the measured density D _i-1 of the previous time is B
= (D _i −D _i−1 ), and A is multiplied by a coefficient f to be the previous correction value, and α is a ratio for performing correction to prevent excess or deficiency. The following relationship holds.

Therefore, the correction value of this time may be corrected according to the ratio α, and the print density may be corrected by the corrected value, and the difference between the reference density D _s and the actually measured density D _{i of} this time may be E _i = ( D _s −
D _i ), and the corrected value corrected this time is C _i , it is given by the following equation.

It should be noted that α is calculated as a moving average in accordance with the repetition of the number of times of measurement m, and the latest value thereof may be used. If the correction value for each blade is different for the same color, these median values may be used.

Therefore, the CPU 41 memorizes each data such as D _s , D _i-1 , D _i, etc.
The correction values C _i corrected by the calculation of the equation (3) are sequentially stored in 42, and the printing machine 5 is controlled in accordance with the correction values C _i , so that the correction of the printing density can be performed promptly without excess or deficiency. As a result, the responsiveness of the correction control status is improved, and the amount of defective printing is significantly reduced.

However, the configuration of FIG. 1 can be freely applied to various configurations in which selection according to the situation is arbitrary.

〔The invention's effect〕

As is clear from the above description, according to the present invention, the correction value correction using the ratio according to the actual printing condition optimizes the correction status of the print density, and the improvement in the responsiveness of the correction control results in the occurrence amount of defective printing. Is significantly reduced,
A remarkable effect can be obtained in correction of print density of various printing machines.

[Brief description of drawings]

FIG. 1 shows an embodiment of the present invention, FIG. 1 is a diagram showing a correction situation, and FIG. 2 is a block diagram showing a configuration. 1 ... reference paper, 2 ... DM (densitometer), 3 ... sample paper, 4 ... control circuit, 5 ... printing machine, 41 ... CPU (processor), 42 ... MEM (memory), D _s …… Standard density, D
_i-1 , D _i ... Measured concentration.

Claims (1)

(57) [Claims] 1. A printing density of a printing surface is measured, a correction value C is obtained from a difference (D _s -D) between a reference density D _s and an actually measured density D, and an ink of a printing machine is printed according to the obtained correction value C. In the method of controlling the supply amount and correcting the print density, the difference A = (D _s −) between the reference density D _s and the previously measured density D _i−1.
D _i-1 ) is divided by the difference B = (D _i −D _i-1 ) between the measured density D _{i of} this time and the measured density D _i-1 of the previous time to obtain the ratio α = A / B. Difference between the reference density D _s and the actually measured density D _i this time E _i = (D _s −D _i ).
And a correction value C _{i of} this time is calculated from the ratio α, and the ink density is controlled according to the calculated correction value C _i .