JPH04250041A - Color tone control device - Google Patents

Abstract

PURPOSE:To ensure that a color tone can be automatically maintained in an optimal state during printing process by detecting solid print density and half- tone density govern the color of printed matter and controlling an ink feed quantity and a wetting water feed quantity respectively based on the detection results. CONSTITUTION:The densities of solid print and half-tone print monitoring strips printed on printed matter are detected using a device 2. In addition, at a point of time when satisfactory printed matter which becomes a control target is obtained, a color density detected for each print monitoring strip is stored as a target color density using a device 4. In addition, the detected color density is compared to the stored target color density and the devidation is calculated using a device 5. On the other hand, an ink correction quantity and a wetting water correction quantity are calcualted using a device 6 based on the calculated deflectin valve and a function. Further, the ink feed quantity and the wetting water quantity are adjusted using each device 7, 8 based on the calculated ink and wetting water correction quantity. Thus the color tone is maintained automatically at an optimal state during printing process.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a color tone control device applied to an ink supply device and a dampening water device of a printing machine.

0002

[Prior Art] In multicolor printing, ink viscosity, printing pressure, dampening water content in ink, etc. change due to changes in ambient temperature and humidity, temperature changes due to heat generated by printing machine rollers, etc. , As a result, the color tone of printed matter changes over time. When this change in color tone becomes large and the difference in color from the sample print (for example, a proof print) becomes extreme, it is considered to be a defective color tone. To prevent this poor color tone, the operator constantly monitors the entire surface of the printed material during printing and makes adjustments to maintain the color tone.

A color tone control device that automates this color tone adjustment work has already been proposed. This color tone control device controls only the ink supply amount based on density fluctuations of the print monitoring strip.

0004

SUMMARY OF THE INVENTION The conventional color tone control device has the following problems. That is, the varying color tone is affected not only by the variation in the amount of ink supplied, but also by the variation in the amount of dampening water supplied. Further, the tendency of the variation of the solid density and halftone dot density with respect to the variation of the ink supply amount is different from that of the variation of the solid density and halftone dot density with respect to the variation of the dampening water supply amount. However, in the conventional color tone control device, only the ink supply amount is controlled based on density fluctuations of the print monitoring strip, making it difficult to maintain the optimum color tone.

The present invention has been proposed in view of the above-mentioned problems, and its purpose is to provide a color tone control device that can automatically maintain the color tone in an optimal state during printing. .

[0006]

[Means for Solving the Problems] In order to achieve the above object, the color tone control device of the present invention detects the density of a solid color printed on a printed matter and a print monitoring strip of halftone dots during printing. a detection device, a target color density storage device that stores the color density detected for each of the print monitoring strips as a target color density at the time when a good printed material that is the target of control is obtained, and a color density detection device that detects the color density. a color density difference calculation device that compares the detected color density and the target color density stored in the target color density storage device and calculates the deviation; an ink and dampening water supply amount correction calculation device that calculates the ink correction amount and dampening water correction amount using a function that has been calculated; and a calculation device that adjusts the ink supply amount based on the calculation results from the calculation device to make the above deviation zero. The apparatus includes an ink supply amount adjustment device and a dampening water supply amount adjustment device that adjusts the dampening water supply amount based on the calculation result from the calculation device to make the above-mentioned deviation zero.

[0007]

[Operation] The color tone control device of the present invention is configured as described above, and detects the solid density and halftone density that control the color of printed matter, and adjusts the amount of ink supply and dampening water based on the detection results. The color tone is adjusted to the target color tone by controlling the supply amount.

[0008]

[Embodiment] The color tone control device of the present invention will be explained using an embodiment shown in FIGS. 1 to 5. In FIGS. 1, 2, and 3, 1 is a color line camera, 2 is a color density detection device for each ink key,
3 is the target value input switch, 3' is the target value input switch 3
4 is a target color density storage device, 5 is a color density difference calculation device, 6 is a calculation device for correcting ink and dampening water supply amount, 7 is an ink supply amount adjustment device, and 8 is a dampening water supply amount Adjustment device, 9 in Figure 3 is a light source, 10 is an optical fiber, Figure 2
11 in FIG. 5 is a printed matter, 12 is a print monitoring strip,
4, 13 is the ink key width, 14 is the solid area, 15 is the halftone dot area, 16 is the black solid area, 17 is the black halftone area, 18 is the indigo solid area, 19 is the blue halftone area, and 20 is the indigo dot area. The red solid area, 21 is the red halftone dot area, 22 is the yellow solid area, 23 is the yellow halftone area, and 24 in FIG. 3 is the impression cylinder.

Color detection is performed on the printed paper 11 on the impression cylinder 24 after printing. Light source body 9 consisting of a xenon lamp etc.
The light passes through the optical fiber 10 and illuminates the surface (printing surface) of the printing paper 11. The optical fiber 10 guides light into a limited narrow space inside the printing machine and creates a band-shaped light that matches the detection area of the color line camera 1. As shown in FIG. 3, the optical fiber 10 is installed so as to irradiate light at an angle of about 45 degrees with respect to the normal line from the printing surface of the printing paper 11.

On the other hand, the color line camera 1 uses printing paper 1
It is installed so as to receive the reflected light from the printed surface of No. 1. As shown in FIG. 2, the detection area of the color line camera 1 is the entire width in the width direction and 1 mm to several mm in the running direction. In other words, the detection area for one line is (print paper width) x (1 m
m to several mm). Inside the color line camera 1, there are three light-receiving sections with blue, green, and red filters. An electrical signal is generated for each line.

[0011] Each minute area for each line (approximately 1,000 pieces)
Electric signals corresponding to the magnitudes of the blue, green, and red densities are sequentially sent to the color density detection device 2. As the printing paper 11 travels, the detection area of the color line camera 1 changes sequentially. Then, as described later, the position of the print monitoring strip section 12 on the printing paper 11, whose position and size from the paper edge and information on whether it is a solid area or a halftone dot is known, is detected, and printing is performed every 13 ink key widths. The average value of the color density of the strip (solid area 14 and halftone area 15) is sent to the color density detection device 2 and stored separately.

The color density detection device 2 detects four colors (black, indigo, red,
In order to correspond to printing (yellow), the color densities of three colors, blue, green, and red, are detected, but here, the explanation will be limited to one color. Therefore, the color density in the following description is limited to only one that corresponds to the main absorption wavelength of a certain ink (for example, if the ink is yellow, the color density is blue). Even in the face of disturbances such as changes in machine speed, a synchronization device is required to detect the position of the print monitoring strip printed on the printing paper 11 and to store the density signal in the same memory location at all times. The synchronization signal is, for example, a rotary encoder (R/
It can be produced from E). The rotary encoder (R/E) has two types of pulse signals: 1 pulse/rotation and 1.500 pulses/rotation, and each is synchronized with the input start signal (aligned with the front edge of the printing paper 11) and subdivision. Signal. By a general method using such synchronization signals, signals are captured on the printing surface of the printing paper 11 at a pitch of about 1 mm. At this time, the pick-up position will not shift even if the machine speed changes.

If the color density signal detected in this way is for a good printed matter (OK sheet) that is the control target, the target value input switch 3 in FIG.
is connected to the target color density storage device 4 and stored therein. On the other hand, if the calculated average color density signal is for the printed matter 11 to be controlled,
The target value input switch 3 is connected to the B side, and the target value is sent to the color density difference calculation device 5. Note that this target value input switch 3
is installed, for example, on a color booth, and the switching is left to the print operator.

When the target value input switch 3 is connected to the A side, the switch 3' is automatically separated from the contact point C, and no signal is sent to the color density difference calculation device 5, so that the ink supply amount and moisture content are Water supply is not regulated. On the other hand, when the target value input switch 3 is connected to the B side, the switch 3' is automatically connected to the contact C, and the target color density signal stored in the target color density storage device 4 is changed to the color density difference. It is sent to the arithmetic unit 5.

Focusing on the movement during the control period, switches 3 and 3' are connected to contacts B and C, respectively, and the dot density DV signal and dot density of the strip portion printed on the printed material 11 to be controlled are controlled. The DR signal and the corresponding target solid density DV' signal and halftone dot density DR' signal are sent to the color density difference calculation device 5. Then, the color density difference calculating device 5 calculates the difference between the two color densities.

[0016]ΔDV=DV−DV'ΔDR=D
R-DR' The calculated color density difference signal is sent to an arithmetic unit 6 for correcting the amount of ink and dampening water supplied. Next, the contents of the calculation performed by the calculation device 6 for correcting the amount of ink and dampening water supplied will be explained. As already mentioned, the tendency of fluctuations in solid density and halftone dot density with respect to fluctuations in ink supply amount is different from that of fluctuations in solid density and halftone dot density with respect to fluctuation in dampening water supply amount.

[0017] Therefore, these relationships are expressed by the following functions,
The ink correction amount ΔI and the dampening water correction amount ΔW are determined from the solid density difference ΔDV and the dot density difference ΔDR. ΔI=F1(ΔDV, ΔDR) ΔW=F2(ΔDV, ΔDR) As an example of this function, assume the following equation. Note that the constants K1 to K4 are determined experimentally.

ΔI=F1(ΔDV, ΔDR)=K1・ΔD
V +K2 ・ΔDR ΔW=F2(ΔDV , Δ
DR )=K3 ・ΔDV +K4 ・ΔDR Then, the ink correction amount ΔI and the dampening water correction amount ΔW are calculated from the solid density fluctuation amount ΔDV and the halftone density fluctuation amount ΔDR, and the signals obtained at that time are sent to the ink supply amount adjustment device 7. and the dampening water supply amount adjustment device 8, and correct each of them, thereby adjusting the color tone of the printed material 11 to the target color tone.

[0019] It is also possible to apply this to multicolor printing. As an example, consider printing in four colors: ink, indigo, red, and yellow. In order to perform color tone control using this method in four-color printing, the following steps can be performed. As shown in FIG. 4, the print monitoring strip is divided into eight parts 16 to 23 within the width 13 of one ink key, and solid and halftone dots are printed for every four colors. For example, 16 is solid black, 17 is black halftone, 18 is blue solid, 19 is blue halftone, 20 is red solid, 21 is red halftone, 22 is yellow solid, 23 is yellow halftone. Print each dot.

The position of each strip and information about each strip (area ratio of color and halftone dots) are stored in the color density detection device 2. However, solid and halftone density shall be determined based on the main absorption wavelength of each ink.

[0021]

Effects of the Invention As described above, the color tone control device of the present invention detects the solid density and halftone density that govern the color of printed matter, and adjusts the ink supply amount and dampening water supply amount based on the detection results. Since the color tone is adjusted to the target color tone by controlling the color tone, it has the effect of automatically maintaining the color tone in an optimal state during printing.

[Brief explanation of the drawing]

FIG. 1 is a block diagram showing an embodiment of a color tone control device according to the present invention.

FIG. 2 is an explanatory diagram showing a color density detection range of printing paper.

FIG. 3 is a side view showing the detection means.

FIG. 4 is a plan view showing an example of a print monitoring strip on printed paper.

FIG. 5 is an explanatory diagram showing an example of a print monitoring strip for four colors.

[Explanation of symbols]

2 Color density detection device 4 Target color density storage device 5 Color density difference calculation device 6 Calculation device 7 for correcting ink/dampening water supply amount
Ink supply amount adjustment device 8 Dampening water supply amount adjustment device

Claims (1)

[Claims] 1. A color density detection device that detects the density of a print monitoring strip of solid and halftone dots printed on a printed product during printing, and a color density detection device that detects the density of a print monitoring strip of solid and halftone dots printed on a printed product, and a color density detection device that detects the density of a print monitoring strip of solid and halftone dots printed on a printed product, and a color density detection device that detects the density of a print monitoring strip of solid and halftone dots printed on a printed product, and a color density detection device that detects the density of a print monitoring strip of solid and halftone dots printed on a printed product. a target color density storage device that stores the color density detected for each strip as a target color density; and a target color density storage device that stores the detected color density detected by the color density detection device and the target color density stored in the target color density storage device. A color density difference calculation device that compares and calculates the deviation, and an ink/dampening solution that calculates the ink correction amount and dampening water correction amount based on the calculation results from the same color density difference calculation device and a predetermined function. A calculation device for correcting the supply amount, an ink supply amount adjustment device that adjusts the ink supply amount to zero the above deviation based on the calculation result from the calculation device, and an ink supply amount adjustment device that adjusts the dampening water supply amount based on the calculation result from the calculation device. A color tone control device comprising: a dampening water supply amount adjusting device that adjusts the above deviation to zero.