JPS6349161B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a calibration method in a printing plate pattern area ratio meter that measures the area of an image area (picture area) from a printing plate for an offset printing machine.

By the way, the method to measure the pattern area is as follows.
In addition to the method of measuring the pattern area from a printing plate, there are methods that detect proofs, prints from this machine, reflective originals, transparent originals, etc. Furthermore, there are some printers that utilize this measured value to check the density of printed matter during operation of the printing press and perform feedback control, and others that preset the ink supply amount before printing. However, in a normal printing plate, the pattern on the printing plate is a pattern formed by arranging a plurality of originals at predetermined positions and printing them. Therefore, when measuring objects other than printing plates and printed matter from this machine,
The disadvantage is that after measuring the area of each pattern, the measurement data must be compiled based on the layout on the printing plate. On the other hand, if you measure a printing plate or printed matter from this machine, you can use the measurement data immediately, but when you obtain measurement data from printed matter from this machine, the measurement must be performed after printing has started. This is a feedback control system that corrects fluctuations caused by disturbances during printing. On the other hand, when obtaining measurement data from a printing plate, the purpose is to preset the opening degree of the ink adjustment key before starting printing, and to print a good product from the time printing starts.

Here, as an example of a device that uses a printing plate as a measuring object, the printing plate is wound around a cylinder and rotated at high speed.
There are methods that measure the average afterimage for each zone (for example, Japanese Patent Publication No. 47-42205), or scan the original plate (printing plate) of an offset printing machine to obtain the number of pulses corresponding to the area of the image area. A device that adjusts the ink supply amount (for example, Japanese Patent Application Laid-open No. 48-53804) detects and integrates the image lines on the printing plate for each ink adjustment key, and uses an auxiliary printing plate to detect the amount of reflected light in the non-image area. , calculates the signal of only the image area from the detection signal of the printing plate,
There are methods that adjust the amount of ink by converting it into a value corresponding to the area of the image (for example, Japanese Patent Laid-Open No. 49-67714), and there are also methods that scan the original in the vertical direction and measure the occupancy of the image in the width direction of the original. A device that measures and controls the ink supply amount at the ink source roller section (for example, Japanese Patent Application Laid-Open No. 51-2505) scans a photoelectric detection device vertically at a predetermined position in the horizontal direction of the printing surface or plate surface. There is a method that calculates the total amount of ink and adjusts the amount of ink (for example, Japanese Patent Publication No. 47405 of 1983).
However, since none of these devices that detect printing plates can accurately detect printing plates, they have not become practical.
That is, after contact exposure of a transparent film original is carried out, the printing plate is normally processed according to the processing steps shown in FIG. 1, which will be explained next. Here, the original image processing of the normally used positive type printing plate (step S1)
This is done to remove the photosensitive layer in areas exposed to light (non-image areas) and make it desensitized (to prevent ink from adhering to the surface), but some parts remain even after development. An erasing liquid is applied to only that part of the unnecessary photosensitive layer to dissolve it (step S3). Next, the printing plate is dried (step S4), a surface preparation liquid is applied to the entire printing plate (step S5), and the printing plate is dried by buff drying so that no surface preparation liquid remains on the printing plate surface (step S7). ). These surface smoothing treatment and buff drying are preparation steps for the burning (high temperature heating) treatment, and by subsequently performing the burning treatment (step S8), the printing durability of the printing plate is improved by two to three times. Finally, a so-called gumming treatment (step S10) is performed for the purpose of protecting the surface of the non-image area and further increasing hydrophilicity, thereby completing the printing plate treatment process. In such processing steps, burning treatment is extremely effective in improving the printing durability of printing plates, but
Since printing plates are heated at high temperatures of 250℃ to 300℃, as a result, ordinary printing plates based on hard aluminum plates undergo thermal deformation, and even after cooling, permanent deformation occurs and the flatness of the plate surface deteriorates. Resulting in. Therefore, when detecting the amount of reflected light to determine the picture area from such a printing plate, the amount of reflected light changes not only depending on the picture area but also depending on the degree of unevenness and misalignment of the printing plate. As a result, accurate detection accuracy cannot be obtained and the ink supply amount cannot be set correctly.

In addition, in places that have a large number of printing machines of various types, it is common for many types of printing plates to be processed in the printing plate process, and the pattern area meter from the printing plate is It is preferable to use the measuring device integrated with the printing plate line at the printing plate site, and to measure data for ink adjustment of multiple printing presses with one measuring device, rather than using the measuring device integrated with the printing press at the printing plate site. Therefore, it is an object of the present invention to provide a calibration method for a printing plate pattern area ratio meter that satisfies such requirements and is free from the above-mentioned drawbacks.

This invention will be explained below.

In this invention, as shown in FIG. 2, a printing plate 20 is fixedly mounted below the movable photoelectric detection devices 10 arranged in a line, and the photoelectric detection devices are transported by a conveying device to be described later. By moving the printing plate 10, detection scanning of the printing plate 20 is performed linearly.

However, in the printing plate 20 used here,
A calibration mark 23 in a rectangular or other shape is placed at an arbitrary position on the edge 21 or edge 22 of the printing plate (or any part that does not adversely affect printing).
is attached, or a solid part in the drawing area is set as the mark, and this calibration mark 23 distinguishes between the non-printing area (A1 grain area) and the drawing area (picture area). It has become possible to distinguish between The photoelectric detection device 10 also includes a pair of parallel cylindrical fluorescent lamps 11 that can form a linear irradiation surface.
and 12, and photoelectric detectors 13 of S ₀ , S ₁ , S _{2 .} . . , S _o arranged in a line as shown in FIG. It is provided. However, this photoelectric detector 13 (S ₀
~S _o ) circuit configuration is shown in Figure 4, printing plate 2
A photodiode PD that receives reflected light from 0 and converts it photoelectrically, an operational amplifier OP that uses this output as one input (the other input is grounded),
It consists of a resistor R and a capacitor C connected between the input and output of this operational amplifier OP. The structure of the photoelectric detector 13 (S ₀ to S _o ) is as shown in FIGS. 5A and 5B, in which a photodiode PD for photoelectric detection is attached to the upper end of a cylindrical shielding box 14.
At its lower end there is a slit 15 that receives reflected light.
is provided. Thus, a light shielding box 17 is provided which encloses the slit 15 portion of the shielding box 14, shields the fluorescent lamps 11 and 12, and is provided with a slit 16 at the bottom for receiving reflected light from the printing plate 20. has been done. In addition, the shielding box 14
A partition plate 18 for partitioning the optical path is provided between the detection part of the calibration mark 23 and the part for detecting the pattern.

Here, the actual configuration of the photoelectric detection device 10 is shown in FIGS. 6A, B, and C, and the front panel 71 of the measuring device main body 70 is a vertical slope with an inclination. Guide rails 72 and 73 are provided at the upper and lower ends, respectively, and a convex stage 74 for mounting the printing plate 20 is arranged at the center of the front panel 71. In addition, the printing plate 20 has pins 75~
The stage 74 is positioned by a suction device 38, and the stage 74 is attracted to the stage 74 by a suction device 38. Further, the stage 74 is made of a porous sheet or a plate having a large number of small holes. A scanning device 10A having a box-like concave structure and including the above-described photoelectric detection device 10 and a necessary circuit configuration is slidably disposed between the guide rails 72 and 73. The printing plate 20 is inserted between the scanning device 10A and the stage 74, and the scanning device 10A is moved in the M and N directions shown in the figure by driving the scanning rope 31. Therefore, the photoelectric detection device 10 disposed in the lower part of the printing plate 20 scans the printing plate 20 in a line. Further, near the side of the stage 74 on the front panel 71, there is an operation input device, such as a keyboard 47, for specifying the operation of the scanning device 10A, and an output device, for example, for displaying the results of scanning by the scanning device 10A. A printer 48 is provided.

As shown in the figure, the scanning mechanism of the scanning device 10A has its top 10B fixed to the scanning rope 31 wound around a driving roller 91 and an auxiliary roller 92 arranged at both ends of the upper part of the front panel 71. By rotating the drive roller 91 with a separate drive motor 93, the guide rail 72,
73 in the M and N directions. Note that a rotary encoder 36 is attached to the rotation shaft of the drive roller 91 to detect the position of the scanning device 10A. Furthermore, stage 74
A suction device 38 consisting of a suction pump or the like is provided below the printing plate 20 mounted thereon.

On the other hand, the arithmetic processing unit 40 that calculates the picture area from the detection signal includes an amplifier circuit 41 (A ₀ to A _o ) for amplifying the detection signal from the photoelectric detector 13 for each detection element, as shown in FIG. , a multiplexer 42 for selectively outputting the signal from this amplifier circuit 41 according to an arithmetic processing program, and a multiplexer 42 for converting the output of this multiplexer 42 into a digital signal.
AD converter 43 and CPU (microprocessor)
44, a ROM (read only memory) 45 and a RAM (random access memory 46) as storage devices, a keyboard 47 for inputting data and other necessary numerical values, and a printer 48 for printing out the results of arithmetic processing. , the above AD converter 4
3 and an input/output control device 49 that controls input/output with the CPU 44 and others.
9, CPU 44, ROM 45, RAM 46, keyboard 47, and printer 48 are mutually connected via a bus. Further, the output of the rotary encoder 36 is input to the CPU 44 via a reading circuit 50 and a bus.

In such a configuration, if the relative positional relationship between the photoelectric detector 10, the fluorescent lamps 11 and 12, which detect the amount of reflected light from the printing plate 20, and the printing plate 20, which is the detection target, is set as follows, the burning process can be performed. Detection errors due to unevenness on the surface of the printing plate caused by such causes can be reduced. That is, the above-mentioned "relative positional relationship" means that the fluorescent lamps 11 and 12 are arranged parallel to the printing plate 20 as shown in FIG. 0.35-0.70 times the distance (2K), more preferably
Fluorescent lamp 11 by a distance (x) in the range of 0.4 to 0.6 times,
12 as a reference position, a detection area P around a position on the printing plate surface of the printing plate 20 that is equidistant from the two fluorescent lights 11 and 12, and only the reflected light from the detection area P is received. This refers to the optimal positional relationship for measurement in which the photoelectric detector 10 is placed opposite the printing plate 20 so that The effect of light transmission and reception between the photoelectric detection device 10 and the printing plate 20 having such a relative positional relationship will now be described. Incidentally, since the fluorescent lamps 11 and 12 are linear light sources, their illumination intensity is inversely proportional to the distance from the light source. In other words, in the case of a point light source, it is inversely proportional to the square of the distance from the light source, but in the case of a line light source, the illuminance of a certain surface is considered to be a linear light source gathered in a line, and the illuminance of a certain surface is inversely proportional to the square of the distance from the light source. If an integral calculation is performed assuming that the illuminance is the sum of the contributions of all point light sources to the light source, the illuminance is inversely proportional to the distance from the light source. On the other hand, the illuminance of a surface that is not perpendicular to the projected light beam is sin θ times the illuminance of the surface that is perpendicular, where θ is the angle between the surface and the perpendicular surface. Therefore, the illuminance I in the detection area P in FIG. 8 is I _(x) = A·x/K ² +x ² (1) where A is a proportionality constant. Now, assuming that the printing plate 20 is placed at a predetermined position x ₀ , and if the positional deviation due to unevenness on the surface of the printing plate 20 is Δx ₀ , then the value when x=x ₀ in the above equation (1) is , there is a difference in illuminance corresponding to the difference from the value when x=x ₀ +Δx ₀ , and a measurement error corresponding to this difference will occur. Incidentally, the illuminance I _(x) is a function having a maximum value at x=K as shown in FIG. 9, and near the maximum value, the change in the illuminance I _(x) for the same positional deviation Δx ₀ becomes small. Therefore x=K
If the printing plate 20 is installed at a position where the detection area P is detected by the detector 10 that detects the detection area P, accurate measurement can be performed even if the printing plate 20 has irregularities. Also, 0.8K<x<1.2K,
In other words, even in the range of 0.4×2K<x<0.6×2K, the characteristics are almost linear, allowing highly accurate measurement.

The operation of such a configuration will be explained with reference to the flowchart of FIG.

Place the printing plate 20 on the stage 74 via pins 75 and 76, and turn on the power switch (step S).
1), the suction device 38 operates and the printing plate 20
is closely fixed to the stage 74, the fluorescent lights 11 and 12 are turned on, and the printing machine number and, for example, front printing or back printing in the case of a blanket-to-blanket type printing machine, are entered from the keyboard 47 ( Step S2). Data set in the ROM 45 is set by these input data. Such RAM46 or ROM45
The data is the plate size (for example, 1310mm x
1050mm, 1160mm x 940mm...), number of ink adjustment keys (e.g. 32, 50...), key spacing (e.g. 30
mm, 40 mm...), the distance between the key and the edge of the plate (for example, 5 mm, 10 mm...), the distance between the printing effective area and the edge of the plate (for example, 22 mm from top to bottom, 20 mm from left to right...), etc. As a result, the usage range of the photoelectric detector 13 (S ₁ to S _k in FIG. 3), the spacing and number of ink adjustment keys, etc. are set (step S3), and by pressing the measurement start switch, the motor (not shown) is activated. is driven, and this motion is transmitted to the scanning rope 31 through a gear mechanism, and the scanning device 10A
The scanning device 1 is moved in the M direction or N direction in Figure B.
The photoelectric detection device 10 built in 0A is the printing plate 20
Detection scanning is performed on the surface of Note that the scanning position of the photoelectric detection device 10 is determined by the rotary encoder 36.
is detected by the CPU via the reading circuit 50 and the bus.
44, and the timing of the detection position and the detection scanning movement are matched. Here, the irradiated light from the fluorescent lamps 11 and 12 in the photoelectric detection device 10 passes through the slit 16 and reaches the printing plate 20 (or the stage 74), and the reflected light passes through the slit 16 again, and then passes through the shielding box 14. The light reaches the photodiode PD through the slit 15 and is converted into an amount of electricity corresponding to the amount of light. In addition, the photoelectric detector S ₀ in FIG. 3 detects the non-image area and the calibration mark 23 in order to calibrate the upper and lower limits of the amount of reflected light, and the photoelectric detector S _k detects the non-printing area and the calibration mark 23 in order to calibrate the upper and lower limits of the amount of reflected light. It is used to take in only the detector output as data.

Thus, when the position information output from the rotary encoder 36 matches the edge position information of the printing plate set during the program, the amount of reflected light from the printing plate 20 is detected by the photoelectric detection device 10 (step S4), and the amount of light reflected by the printing plate 20 is detected by the multiplexer 42. The detected data selected and output according to the program is converted into digital data by the AD converter 43 and then input to the register of the CPU 44 via the input/output control circuit 49 and the bus (step S5). When data input for a portion corresponding to one ink adjustment key is completed (step S6), the data is transmitted from the register of the CPU 44 to the RAM 46 (step S7). At this time, the calibration mark 2
3 is processed in the same way. In this way, the output from each photoelectric detector 13 is selectively outputted by the multiplexer 42, and after AD conversion, is stored in the address of the RAM 46 corresponding to the detection target (calibration mark, picture).

The details of the calibration are as follows.

Every time the scanning device 10 advances, for example, by 3 mm, the photoelectric detector S ₀ (or other photoelectric detector) detects the buttock 2.
2 (or a portion that does not adversely affect the grip 21 or printing), each time the amount of reflected light is measured, the average of the past measurements, for example four measurements, is calculated and stored.

Here, without calculating the average value of the past several times, for example, when the scanning device 10 advances by 3 mm, the amount of reflected light from the end of the bite 22 (or the end of the bite 21 or a portion that does not adversely affect printing) is measured using the photoelectric detector _S0 . If the measured value is X _i , the maximum value AD _nax from X ₁ to X _o is AD _nax = MAX (X ₁ , X ₂ ..., X _o ) ...(2), and from X ₁ The minimum value AD _nio up _{to X o} is _{AD nio} = MIN ₍ X ₁ , Later data processing is performed as the amount of reflected light. However, 1≦i≦n (4) where n is the total number of measurements. However, with this method, the effects of light disturbance and reflection appear directly on AD _nax and AD _nio , resulting in deterioration of measurement accuracy.

Therefore, in this embodiment, each time a measurement is performed, the measured value X _i and the three previous measured values X _i-1 ,
Calculate the average value of the measurement values for a total of four times (this is arbitrary, the more the better) of X _i-2 and X _i-3 , set this as Y _i , and set the maximum value AD _nax of Y _i and Minimum AD _nio
seek. That is, Y _i =X _i +X _i-1 +X _i-2 +X _i-3 /4 (5) are sequentially determined and compared with the maximum and minimum values so far.
In other words, AD _nax = MAX (Y ₄ , Y ₅ , ..., _Yo ) ...(6) AD _nio = MIN (Y ₄ , Y ₅ , ..., _Yo ) ... (7) and perform the following data processing. used for

That is, the photoelectric detectors in the detection area are numbered S ₁ to S _k in order from the bottom, and the positions of the detection head are 1 to m when measuring, for example, every time it moves 3 mm.

However, if m is the key pitch, then m≦l/
It is the largest integer that satisfies 3. Then, the output of each sensor at each position is Zij (1≦i≦k, 1≦
j≦m), the average value of the output Zij is becomes. The values for the other keys are similarly determined and stored in sequence. After measuring the number of all ink adjustment keys, the area ratio R is Find it with In this case, the brightest part is 100%,
The darkest part is calculated as 0%, but in actual use, the opposite is preferable, so it is displayed as R'=100-R(%) (10).

This makes it possible to remove the effects of light disturbance and reflection, improving measurement accuracy.

After the area ratios are calculated for all the ink adjustment keys, they are printed out by the printer 48 (FIG. 11).

As described above, the measuring device based on the calibration method of the present invention can be used regardless of differences in printing plate processes, printing plate brands, lots, and sizes, and can also be used to It is possible to accurately measure the pattern area without being affected by thermal deformation distortion, and it is also possible to perform measurements corresponding to the width and number of ink adjustment keys that differ depending on the type of printing press used. Therefore, a measuring device is not required for each printing press, and only one device needs to be installed on the printing plate line.Also, because the measurement is taken from the printing plate, it is different from the measurement from a transparent original (film original), etc. , the device is simple and low-cost because it does not require processing of measurement data regarding the layout of the pattern, and the relative position between the printing plate and the detection device is less susceptible to mechanical errors in the device or deformation of the printing plate; Highly accurate measurement becomes possible. Furthermore, in-line automatic measurement on the printing plate line is also possible, and the workload of measurement is small. Therefore, the image area measurement data can not only improve the operating rate of the printing press by presetting the ink adjustment key at the start of printing, and also have the effect of reducing defective prints, as well as help prepare special color inks. It can be applied in many ways, such as estimating the amount of water and reducing fuel consumption by setting the optimal conditions for off-transfer dryers.

As described above, the present invention combines the measured values of the amount of reflected light at each measurement point set at a predetermined pitch in the direction of movement of the scanning device and the measured value of the amount of reflected light at a predetermined number of other measurement points immediately before each measurement point. Since the average value is calculated and the average value is used to calibrate the amount of reflected light in non-image areas or solid image areas, it is possible to eliminate variations in the optical properties of the printing plate or the light source or light-receiving element. This has the effect that it is less likely to be affected by the adverse effects of noise caused by noise, etc., and that the accuracy of calibration can be improved.

In addition, since calibration is performed using the maximum and minimum values of the above-mentioned average values, the calibration mark only needs to be within the movement path of the light receiving element that performs the detection. It also has the effect of reducing sexual tension.

[Brief explanation of the drawing]

Fig. 1 is a flowchart showing the printing plate processing steps, Fig. 2 is a diagram showing the positional relationship between the movable photoelectric detection device according to the present invention and the printing plate, and Fig. 3 is a state of detection scanning by the photoelectric detection device. Figure 4 showing
The figure is a circuit diagram showing an example of the configuration of detection elements in a photoelectric detection device, Figures 5A and B are side and front views showing the schematic structure of the photoelectric detection device, and Figures 6A, B, and C are measurements of the present invention. A front view, a plan view, and a side view showing the external configuration of the device, FIG. 7 is a block diagram showing an example of the configuration of the arithmetic processing device according to the present invention, and FIG. 8 shows the optimal relative positional relationship between the printing plate and the fluorescent light. FIG. 9 is a diagram showing the relationship between distance x and illuminance for explaining the same, FIG. 10 is a flowchart showing an example of the operation of the device according to the present invention, and FIG. 11 is a diagram showing the print according to the present invention. It is a figure which shows an example. 10... Photoelectric detection device, 11, 12... Fluorescent lamp, 1
3... Photoelectric detector, 14... Shielding box, 15, 16... Slit, 17... Light blocking box, 18... Partition plate, 20... Printing plate, 21... Bite, 22... Bite bottom, 23... Calibration mark, 72 and 73...Guide rail, 36...Rotary encoder, 38...Suction device, 40...Arithmetic processing unit, 41...Amplification circuit, 42
...Multiplexer, 43...AD converter, 44...
CPU, 45...ROM, 47...keyboard, 48...
printer, 49...input/output control device, 50...reading circuit, 71...front panel, 74...stage, 75-
78...Pin.

Claims (1)

[Claims] 1. A scanning device including a light source that irradiates light to a detection area of a printing plate for offset printing and a light receiving element that receives reflected light from the detection area, and moves this scanning device to scan the detection area. , a calibration method in a printing plate pattern area ratio meter for measuring the pattern area of the printing plate using a measured value of the amount of reflected light obtained from the output signal of the light receiving element; The amount of reflected light is measured at each of a plurality of measurement points set at a predetermined pitch in the moving direction, and from the time when a predetermined number of other measurement points exist immediately before each measurement point, the amount of reflected light at each measurement point is measured. The average value of the reflected light amount measurement value and the reflected light amount measurement value at a predetermined number of other measurement points immediately before each measurement point is sequentially determined, and the maximum or minimum value of the average value is used to determine the non-printing area or the drawing line. A calibration method in a printing plate pattern area ratio meter, characterized in that calibration is performed using the amount of reflected light from a solid area.