JPH043481B2 - - 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 ratio of an image area (picture area) from a printing plate for an offset printing machine.

2. Description of the Related Art Conventionally, in order to adjust the amount of ink supplied to a printing press, the amount of images included in printed matter has been measured. The amount of this pattern is generally determined in the form of pattern area or pattern area ratio.

By the way, in addition to measuring the pattern area or area ratio from the printing plate, there are two ways to measure it:
Detection targets include proofs, printed matter from this machine, reflective originals, transparent originals, etc. Additionally, there are some printers that use this measured value to check the density of printed matter during operation of the printer to 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 individual 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 the printed matter of this machine, the measurement data can be used immediately, but if you obtain measurement data from the printed matter of 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. , those that calculate only the image area signal from the detection signal of the printing plate and convert it to a value corresponding to the area of the image line to adjust the ink amount (for example, Japanese Patent Application Laid-Open No. 49-67714); Printing that measures the occupancy of the image line in the width direction of the original plate by scanning in the vertical direction and controls the ink supply amount at the ink source roller section (for example, Japanese Patent Application Laid-Open No. 51-2505), and a photoelectric detection device. There is a method (for example, Japanese Patent Laid-Open No. 47-47405) that adjusts the amount of ink by scanning in the vertical direction at a predetermined position in the horizontal direction of the surface or printing plate to determine the total amount of ink.

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, we will explain the development process (switch plate) of the normally used positive type printing plate.
S1) is performed to remove the photosensitive layer in areas exposed to light (non-image areas) and desensitize it (to prevent ink from adhering to the surface), but even after development, some The unnecessary photosensitive layer left behind is dissolved by applying an erasing liquid only to that part (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 surface is dried by buff-drying so that no surface preparation liquid remains on the printing plate surface (step S7). ). These surface treatments and buff drying are done by burning (high-temperature heating).
This is a preparatory step for the 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 the printing plate is heated to a high temperature of 300℃, as a result, ordinary printing plates based on hard aluminum plates undergo thermal deformation, and even after cooling, they become permanently deformed and the flatness of the plate surface deteriorates. . 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. In particular, the present invention reduces the influence of local optical variations due to the position of the printing plate and eliminates the influence of variations in the characteristics of the light receiving elements when calibrating the light amount value for the non-image area. The purpose is to improve measurement accuracy.

To achieve this objective, the present invention provides a method for calibrating the upper limit value of the reflected light amount measurement value used in determining the picture area ratio as the reflected light amount value in the non-printing area. The rear end is used as a calibration area for the reflected light amount value in the non-image area, and the reflected light amount measurement value is the average value of the reflected light amount measurements obtained from each of the plurality of light receiving element outputs in the calibration area. It is characterized in that it is determined as the upper limit value of .

According to the present invention configured in this way, the upper limit of the reflected light amount measurement value used when determining the picture area ratio as the reflected light amount value of the non-image area is the reflected light amount obtained from each of the plurality of light receiving element outputs. Since the average value of the measured values is used and detection is performed from a wide range at the front or rear edge of the printing plate, variations in optical properties due to the position of the printing plate and variations in the characteristics of the light receiving elements are averaged out. Accuracy is improved and
Because the measurement value for calibration is obtained from the photodetector used for image area ratio measurement, the characteristics of the photoreceptor are different from the case where separate photoreceptors are used for image area ratio measurement and calibration. Calibration can be performed without being affected by variations in

Examples of the present invention will be described below.

In this embodiment, as shown in FIG. 2, a printing plate 20 is fixedly attached below movable photoelectric detection devices 10 arranged in a line.
Detection scanning of the printing plate 20 is performed linearly by moving the photoelectric detection device 10 using a conveying device to be described later.

However, in the printing plate 20 used here,
A calibration mark 2 in a rectangular or other shape is placed at an arbitrary position on the bite 21 or the bottom 22 of the printing plate (or a part that does not adversely affect the printing plate).
3 is attached, or a solid part in the print area is set as the mark, and this calibration mark 23 is used to mark the non-print area (Al
It is designed to distinguish between the grain area (grain area) and the drawing area (pattern area). Further, the photoelectric detection device 10 includes a pair of parallel cylindrical fluorescent lamps 11 and 12 that can form a linear irradiation surface, and the fluorescent lamp 11
and photoelectric detectors 13 of S ₀ , S ₁ , S ₂ , . . . , S _o arranged in a line as shown in FIG.
is provided. However, this photoelectric detector 1
3 (S ₀ to S _o ), as shown in FIG. input is grounded)
It consists of an operational amplifier OP, a resistor R and a capacitor C connected between the input and output of the 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. A slit 15 is provided at its lower end to receive reflected light. Therefore, 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 has a slit 16 provided at the bottom for receiving reflected light from the printing plate 20. ing. Also,
A partition plate 18 for partitioning the optical path is provided between the detection part of the calibration mark 23 of the shielding box 14 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. Note that the printing plate 20 has pins 75 to
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 containing the above-mentioned 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 provided a scanning input device for specifying the operation of the scanning device 10A, such as a keyboard 47, and an output device for displaying the results of scanning by the scanning device 10A, such as a printer. 48 are provided.

As shown in the figure, the top part 10B of the transfer mechanism of the scanning device 10A is 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, as shown in FIG.
an amplifier circuit 41 (A ₀ to A _o ) for amplifying the detection signal from each detection element, and this amplifier circuit 41
A multiplexer 42 that selects and outputs signals from the multiplexer 42 according to an arithmetic processing program, an AD converter 43 that converts the output of the multiplexer 42 into a digital signal, and a 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 path.

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 object of detection, is as follows, burning processing etc. Detection errors due to unevenness on the surface of the printing plate caused by this 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. 2K), more preferably 0.35 to 0.70 times
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 plate surface of the printing plate 20 that is equidistant from the two fluorescent lamps 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. 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. By the way, 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 contribution of all point light sources is relaxed, the illuminance will be 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 as follows, where A is a proportionality constant: I(x)=A.x/K ² +n ² (1). Now, assuming that the printing plate 20 is placed at a predetermined position x ₀ , and if the positional deviation due to the unevenness of the surface of the printing plate 20 is Δx ₀ , then the value when X=x ₀ in the above (1), 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, if the printing plate 20 is installed at the position where x=K and the detection is performed using the detector 10 that detects the detection area P, accurate measurement can be performed even if the printing plate 20 has unevenness. I can do it. Also, 0.8K＜x＜
Even in the range of 1.2K, that is, 0.4×2K<x<0.6×2K, the characteristics are almost linear, allowing highly accurate measurements.

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 the pins 75 and 76, and turn on the power switch (step
S1), the suction device 38 is activated and the printing plate 2
0 is tightly fixed on the stage 74, the fluorescent lights 11 and 12 are turned on, and the keyboard 47 is used to display the printing machine number and whether it is front printing or back printing in a blanket-to-blanket printing machine, for example.
(step S2). Data set in the ROM 45 is set by these input data. Such RAM46 or ROM4
The data for 5 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 side to side, etc.). As a result, the usage range of the photoelectric detector 13 (S ₁ to S _k in FIG. 3), the interval and number of ink adjustment keys, etc. are set (step S3), and by pressing the measurement start switch, the motor (not shown) is driven. This movement is transmitted to the scanning rope 31 through a gear mechanism, and the scanning device 10A is moved to the position M in FIG.
The photoelectric detection device 10 built in the scanning device 10A detects and scans the surface of the printing plate 20. In addition, photoelectric detection device 1
The scanning position of 0 is detected by the rotary encoder 36 and sent to the CPU 44 via the reading circuit 50 and the bus, so that the detected position and the timing of 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 to the printing plate 20 (or stage 7).
4) After reaching the top, the reflected light passes through the slit 16 again, and further passes through the slit 15 of the shielding box 14, and reaches the photodiode PD, where it 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 calibration mark 23 that performs the calibration at the lower limit of the amount of reflected light, and sets the value of this calibration mark 23 as the calibration value of the solid area of the image, which is the lower limit of the amount of reflected light. . In addition, printing plate 2 for offset printing
Normally, as shown in FIG. 11, areas 201 and 202 of a certain width from the front and back ends are non-printing areas. Calibration value of the drawing area. That is, the area 201 or 20
The output data of the scanning device 10 corresponding to No. 2 is taken as the calibration value of the non-image area.

Furthermore, detection scanning of the effective area is performed as follows.

When the position information output from the rotary encoder 36 matches the edge position information of the printing plate set during programming, the amount of reflected light from the printing plate 20 is detected by the photoelectric detection device 10 (step S4), and the multiplexer 42 Therefore, the selected output detection data 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 the data input for the portion corresponding to one ink adjustment key is completed (step S6), data is transferred from the register of the CPU 44 to the RAM 46.
The data is transmitted to (step S7). At this time,
Calibration mark 23 is similarly processed. 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 calibration method according to the present invention will be described in detail 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), and each time the measurement is performed, 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 by the photoelectric detection unit _S0 . If the measured value is X _i , then the minimum value AD _{nio from} X _i to X _o is AD _nio = MIN (X ₁ , X ₂ , ..., X _o ) ...(2) Later data processing is performed as the reflected light amount of the solid line portion. However, 1≦i≦n (3) where n is the total number of measurements. However, with this method, the effects of light disturbance and reflection appear directly on AD _nio , resulting in a deterioration in measurement accuracy.

Therefore, for each measurement, the measured value X _i and the three previous measured values X _i-1 , X _i-2 , X _i-4
(This is optional, the more the better)
Find the average value of the measured values and set it as Y _i , and
Find the minimum value AD _nio of Y _i . That is, Y _i =X _i +X _i-1 +X _i-2 +X _i-3 /4 (4) are sequentially determined and compared with the previous minimum value. That is, AD _nio = MIN (Y ₄ , Y ₅ , ..., _Yo ) ...(5) is calculated and used for the following data processing.

In addition, the photoelectric detectors in the detection area are numbered S ₁ to S _k in order from the bottom, and the position of the detection head is 1 to S k when measuring, for example, every time it moves 3 mm.
Let it be m. However, m is the largest integer that satisfies m≦l/3, where l is the key pitch. Then, the output of each sensor at each position is Z _ij (1≦
i≦k, 1≦i≦m), the average Z of the output Z _ij is Z = { _k 〓 ⁱ⁼¹ ( _n 〓 ^j=1 Z _ij )}・1/m・k ……(6) becomes. The values for the other keys are similarly determined and stored in sequence.

At this time, as described above, in this invention, the value from the front end or rear end of the printing plate is used as the calibration value for the non-printing area, so the ink adjustment corresponding to the area 201 or 202 in FIG. The value for the key is used in the following data processing as the calibration value for the non-printing area, ie, AD _nax .

After measuring the number of all ink adjustment keys, the area ratio R is R = Z - AD _nio / AD _nax - AD _nio × 100 (%)...
Find it using (7). In this case, the brightest part is 100%,
The darkest part is calculated as 0%, but in actual use it is preferable to do the opposite, so it is displayed as R'=100-R(%) (8).

As described above, the influence of light disturbance and reflection can be removed, and measurement accuracy is improved.

After the area ratios are calculated for all the ink adjustment keys, they are printed out by the printer 48 (FIG. 12).

The measuring device using the calibration method described above is able to detect thermal deformation of printing plates caused by burning treatment, etc., regardless of differences in printing plate processing, printing plate brands, lots, and sizes. It is possible to accurately measure the picture area ratio without being affected by 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 measurement data of the pattern area ratio can not only improve the operating rate of the printing press by presetting the ink adjustment key at the start of printing, and has the effect of reducing the number of defective prints, but also has the effect of reducing the number of defective prints. It can be applied in many ways, such as estimating the amount of preparation and reducing fuel consumption by setting optimal conditions for off-wheel dryers.

In addition, the calibration value of the non-image area is determined by using the average value of the measured amount of reflected light obtained from each of the outputs of a plurality of light receiving elements, and is detected from a wide range at the front edge or rear edge of the printing plate. Therefore, variations in optical properties due to the position of the printing plate are averaged out, improving accuracy, and since the calibration value is determined using a detector that measures the pattern area ratio, it has the advantage of high reliability. ing. moreover,
Since the image area is determined by the average value of a plurality of times, the accuracy is high, and since the minimum value is taken as the calibration value, there are no restrictions on the mounting position of the calibration mark.

[Brief explanation of drawings]

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 a detection element in a photoelectric detection device, FIGS. 5A and 5B are side and front views showing the schematic structure of the photoelectric detection device, and FIGS. A front view and a side view showing the external configuration of the measuring 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 explains the optimal relative positional relationship between the printing plate and the fluorescent lamp. 9 is a diagram showing the relationship between distance x and illuminance to provide an explanation thereof, FIG. 10 is a flowchart showing an example of the operation of the apparatus according to the present invention, and FIG. FIG. 12, which is a diagram showing the position of the line portion, is a diagram showing an example of printing according to the present invention. 10... Photoelectric detection device, 11, 12... Fluorescent lamp, 13... Photoelectric detector, 14... Shielding box, 1
5, 16...slit, 17...shading box, 18...
...Partition plate, 20...Printing plate, 21...Bite, 22
... Biting end, 23 ... Calibration mark, 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, 72, 73... Guide rail, 74 ...Stage, 75-78...Pin.

Claims (1)

[Scope of Claims] 1. A scanning device comprising a light source that irradiates light to a detection area of a printing plate for offset printing, and a detection device that has a plurality of light receiving elements that receive reflected light from the detection area; a transport mechanism for moving a scanning device relative to the printing plate; the scanning device scans the entire detection area by moving the scanning device relative to the printing plate; A calibration method in a printing plate pattern area ratio meter that measures the pattern area ratio of the printing plate using a reflected light quantity measurement value obtained from an output signal, the method comprising When performing calibration for the upper limit value of the reflected light amount measurement value used as the reflected light amount value, the front end or the rear end of the printing plate is used as an area for calibration of the reflected light amount value in the non-image area, The printing plate image area ratio is characterized in that an average value of the reflected light amount measurement values obtained from each of the plurality of light receiving element outputs in the calibration area is determined as the upper limit value of the reflected light amount measurement value. Calibration method for meters.