JPH0381084B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a picture area ratio measuring device for measuring the area ratio of an image area (design part) from a printing plate for an offset printing machine.

By the way, as a method for measuring the picture area ratio, in addition to the method of measuring the picture area ratio from a printing plate, there are methods that detect proofs, prints from this machine, reflective originals, transparent originals, etc. Furthermore, there are methods that utilize this measured value to check the density of printed matter during operation of the printing press and perform feedback control, and methods 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 ratio of each pattern, the measured 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.
A device that measures the average afterimage for each zone (for example, Japanese Patent Publication No. 47-42205) or scans the original plate (printing plate) of an offset printing machine to obtain pulses corresponding to the area ratio 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,
One that adjusts the amount of ink by converting it into a value corresponding to the area ratio of the image line (for example, JP-A-49-67741), and another that scans the original vertically and uses the area ratio of the image line in the width direction of the original. A device that measures the amount of ink and controls the ink supply amount at the ink source roller section (for example, Japanese Patent Application Laid-Open No. 51-2505), a photoelectric detection device is scanned in the vertical direction 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. 47405/1983).

However, since none of these devices that detect printing plates can accurately detect printing plates, they have not been put to practical use.
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 development process 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. Dissolve the unnecessary photosensitive layer by applying 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 preparation treatments 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 can be increased to 2.
~3x improvement. 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 for improving the printing durability of printing plates, but at temperatures of 250℃ to 300℃
As a result, ordinary printing plates based on hard aluminum plates undergo thermal deformation, resulting in permanent deformation even after cooling, and the flatness of the plate surface deteriorates. Therefore, if the amount of reflected light is detected to determine the picture area ratio from such a printing plate, the amount of reflected light will change depending on the picture area ratio, and will also change 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 ratio meter from the printing plate is It is better to use it integrated with the printing plate line at the printing site and measure data for ink adjustment of multiple printing presses with one measurement device, rather than using it integrated with the printing press at the printing site. . Therefore, it is an object of the present invention to provide a picture area ratio measuring device that satisfies such requirements, and particularly to improve the processing speed of measurement.

This invention will be explained below.

In this invention, as shown in FIG. 2, a detection head 10 comprising movable photoelectric elements arranged in a row
A printing plate 20 is fixedly mounted below the printing plate 20, and detection scanning of the printing plate 20 is carried out linearly by moving the detection head 10 using a conveying device which will be described later.

Therefore, the printing plate 20 used here has a calibration mark 23 in a rectangular or other shape on the edge 22 (edge 21 or a part that does not adversely affect printing) of the printing plate. Ori,
Alternatively, a solid part in the drawing area is set as the mark, and this calibration mark 23 is used to distinguish between the non-printing area (A1 grain area) 24 and the drawing area (picture area) 25. It's becoming like that. The detection head 10 also includes a pair of parallel cylindrical fluorescent lamps 11 and 1 that can form a linear irradiation surface.
2, and photoelectric detectors 13 of S0, S1, S2, . . . , Sn arranged in a line as shown in FIG. However, this photoelectric detector (S
As shown in Fig. 4, the circuit configuration of 0 to Sn) includes a font diode PD that receives reflected light from the printing plate 20 and converts it into electricity, and an operational amplifier that uses this output as one input (the other input is grounded). ing)
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 detectors 13, S0 to Sn is as shown in FIGS. is installed to receive the reflected light RP from the printing plate 20, and a photodiode PD is installed on the opposite side of the printed circuit board PC.
A circuit element (for example, a resistor, an operational amplifier, a capacitor) CD is fixed to process the received light signal from the sensor. Therefore, the reflected light is exposed to the lower end of the shielding box 14.
A slit 15 is provided to accept the RP,
Further downward from the slit 15 position, the slit 15 is wrapped and the fluorescent lamps 11 and 1
A light-shielding box 17 is provided at the bottom thereof with a slit 16 for shielding the light RP from the printing plate 20 and receiving the reflected light RP from the printing plate 20. Also, 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 detection head 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 of the front panel 71, respectively, and a printing plate 2 is provided at the center of the front panel 71.
A convex structure and a stage 74 for mounting 0 are arranged. In addition, the printing plate 20 has pins 75 to 7.
The stage 74 is positioned by a suction device 38, and is also attracted to a stage 74 by a suction device 38. Also,
The stage 74 is made of a porous sheet or a plate with a large number of small holes.

Thus, the scanning device 1 has a box-like concave structure, which includes the above-mentioned detection head 10 between the guide rails 72 and 73, and has the necessary circuit configuration built-in.
0A is slidably disposed. The printing plate 20 is inserted between the scanning device 10A and the stage 74, and the printing plate 20 is inserted between the scanning device 10A and the stage 74.
0A as shown in the figure by driving the scanning rope 31,
By moving the printing plate 20 in the N direction, the detection head 10 disposed below 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 11 with a separate drive motor 93, the guide rail 72,
73 in the M and N directions. Note that a rotary encoder 36 for detecting the position of the scanning device 10A is attached to the rotating shaft of the drive roller 91, and a suction pump etc. for sucking the printing plate 20 mounted below the stage 74. A suction device 38 is provided.

On the other hand, as shown in FIG.
Amplification circuits 41, A0 to An for amplifying detection signals from each detection element, and this amplification 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 bus. In addition, DH in Figure 7
A portion of the head 10 is fixed to a printed circuit board PC within the head 10.

In such a configuration, if the relative positional relationship between the detection head 10, 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, it is possible to perform burning processing, etc. Detection errors caused by unevenness on the printing plate surface 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 to 0.70 times, more preferably 0.4
~0.6 times the distance (X) of the fluorescent light 11,1
2 as a reference position, and 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, so that only reflected light is received from the detection area P. Detection head 1
This refers to the optimal positional relationship for measurement in which the printing plate 20 is placed facing the printing plate 20. The effect of light transmission and reception between the detection head 10 and the printing plate 20 in such a relative positional relationship will now be described. By the way, fluorescent light 1
Since 1 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, so 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. When performing integral calculations assuming that it is the sum of the contributions of all point light sources to a surface, the illuminance is inversely proportional to the distance from the light source. On the other hand, the illuminance on a surface that is not perpendicular to the projection light source is sin θ times the illuminance on the perpendicular surface, 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 expressed as 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 X0, and if the positional deviation due to the unevenness of the surface of the printing plate 20 is ΔX0, then in the above equation (1), X=
There is a difference in illuminance corresponding to the difference between the value when X0 and the value when X=X0+ΔX0, and a corresponding measurement error will occur. By the way, illuminance I(X)
As shown in FIG. 9, is a function having a maximum value at X=K, and near the maximum value, the change in illuminance I(X) for the same positional deviation ΔX0 becomes small.
Therefore, the printing plate 20 is installed at a position where X=K, and the detection head 1 is configured to detect the detection area P.
If the detection is performed at 0, even if the printing plate 20 has irregularities, the measurement can be performed with high accuracy. Also, 0.8K<X<1.2K, that is, 0.4×2K<X<0.6×
The characteristics are almost linear even in the 2K range, 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
×1050mm, 1160mm×940mm), number of ink adjustment keys (e.g. 32, 50, etc.), key spacing (e.g.
30mm, 40mm,...), the distance between the key and the edge of the plate (for example, 50mm, 10mm,...), the distance between the effective printing area and the edge of the plate (for example, 22mm from top to bottom, 20mm from side to side)
…) etc. As a result, the usage range of the photoelectric detector 13 (S1 to Sk in Fig. 3), the spacing and number of ink adjustment keys, etc. are set (step
S3), by pressing the measurement start switch, the motor 34 is driven, and the drive roller 91 is driven by the sprocket 32 of the gear mechanism 37, the sprocket 91' of the drive roller 91, and the endless chain 32' stretched thereon, and the scanning The scanning device 10A is moved in the M direction or the N direction in FIG. 6B via the rope 31, and the detection head 10 built in the scanning device 10A is moved.
will detect and scan the surface of the printing plate 20.
The scanning position of the detection head 10 is detected by a rotary encoder 36 and is transmitted via a reading circuit 50 and a bus.
The signal is sent to the CPU 44, and the timing of the detection position and 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 the stage 74), the reflected light RP 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. Note that the photoelectric detector S0 in FIG. 3 detects changes in the amount of light from the light source (fluorescent lamps 11, 12) due to power supply voltage, ambient temperature, etc., and the changes are corrected in subsequent data processing. In addition, the photoelectric detector S0 detects the non-image area 24 and the calibration mark 23 in order to perform calibration between the upper and lower limits of the amount of reflected light, and the photoelectric detector Sk only detects the detector output within the printing effective area. It is used to incorporate as data. Note that the photoelectric detector for performing calibration is not limited to S0 in FIG. 3, and can be freely selected depending on the calibration position.

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 detection head 10 (step
S4), the detection data selected and output by the multiplexer 42 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 the 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 S6).
S7). At this time, the detection data of the calibration mark 23 and the amount of light from the light source are also 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, it is stored in the address of the RAM 46 corresponding to the detection target (calibration mark, pattern, light source).
Rather than storing detection data once, multiple scans are repeated and stored. This makes it possible to reduce the influence of noise-based errors. Then, it is determined whether or not the number of all ink adjustment keys has been imported (step S8), and if the import is complete, after this determination, the calibration and light source light intensity are corrected by arithmetic processing of the data in the RAM 46. , the total picture area, area ratio, and picture area ratio for each ink adjustment key are determined (step S9).
In this case, the processing of the detection data corresponding to the ink adjustment key will be performed according to the printing machine number that has already been set.
This is done by selectively using data such as the ink adjustment key width and number stored in the ROM 45 or RAM 46. The picture area and area ratio thus determined are printed out by the printer 48 (step S10). An example of this stamping form is shown in FIG.

As described above, according to the measuring device of this embodiment, prior to measuring the picture area ratio, the range used for measurement in the plurality of optical sensors S1 to Sn of the detection head 10 is determined based on the preset information set in the ROM 45. Since the pattern area ratio is calculated using the measured value of the amount of reflected light from the set optical sensor, it is possible to improve the processing speed of the measurement.

In addition, the image area ratio can be accurately determined regardless of differences in printing plate processing, differences in printing plate brands, lots, and sizes, and without being affected by thermal deformation distortion of printing plates caused by burning processing. measurements can be made, and measurements can be made that correspond to different ink adjustment key widths and numbers depending on the type of printing press used. Therefore, a measuring device is not required for each printing machine, and only one measuring device needs to be installed on the printing line.
In addition, since measurements are taken from printing plates, unlike measurements from transparent originals (film originals), there is no need to process the measurement data regarding the layout of the image, and the relative position of the printing plate and the detection device cannot be processed. Since it is less susceptible to mechanical errors and printing plate deformation, the device is simple and inexpensive, and enables highly accurate measurements. In addition, since the circuit elements of the detection head are mounted on the support plate inside the detection head, it is easy to downsize the device.Moreover, in the data transmission circuit, the outputs of a large number of optical sensors are selected by a multiplexer, and then the AD Since it is converted and transmitted, it has the advantage of being resistant to noise and requiring fewer transmission lines. In addition, the measurement timing is obtained from the position information signal from the head position detector that detects the position of the detection head during scanning, and the data signal from the data transmission circuit is processed in correspondence with the arrangement position of each ink adjustment key. ,
Since it is now possible to perform measurements while scanning and moving the detection head without fixing it at the measurement position, it is possible to achieve the effect of shortening the measurement time accordingly.
Another advantage is that even if the arrangement interval of the ink adjustment keys is changed, it can be easily accommodated by simply changing the preset information for determining the measurement timing. Furthermore, automatic in-line measurement on the printing plate line is also possible, which reduces the workload of measurement. Therefore, by presetting the ink adjustment key at the start of printing based on the measurement data of the pattern area ratio, it is possible to improve the operating rate of the printing press, which not only has the effect of reducing defective printed matter, but also has the effect of reducing the number of defective printed matter. It can be applied in a variety of fields, such as estimating the amount of preparation in a dryer, and reducing fuel consumption by setting optimal conditions for an off-wheel dryer.

In addition, if the printing plate has a positive type resist layer, the irradiation light should be one with a wavelength around 650 nm, since this layer is usually green in color and this layer collapses in the wavelength range of 350 to 500 nm. It is desirable to do so. By doing so, it is possible not only to avoid collapse of the resist layer, but also to improve the optical contrast between the image area and the non-image area, and to optimize the measured values.

As explained above, according to the present invention, depending on the size of the detection area of the printing plate, the measured values of the amount of reflected light from all the optical sensors are not used, but are limited to the measured values of the amount of reflected light from the minimum necessary number of optical sensors. Since the pattern area ratio is determined using the above method, the processing speed of the measurement can be improved.

Moreover, even for printing plates of different sizes, the pattern area ratio can be accurately measured using the amount of reflected light from the detection area of the printing plate.

[Brief explanation of drawings]

FIG. 1 is a flowchart showing the printing plate processing process, FIG. 2 is a diagram showing the positional relationship between the movable detection head and the printing plate according to the present invention, and FIG. 3 is a diagram showing the state of detection scanning by the detection head. 4 is a circuit diagram showing an example of the configuration of the detection element in the detection head, FIGS. A front view, a plan view, and a side view showing an example of the external configuration of a measuring device according to the invention, FIG. 7 is a block diagram showing an example of the configuration of an arithmetic processing device according to the invention, and FIG. FIG. 9 is a diagram for explaining the relative positional relationship, FIG. 9 is a diagram showing the relationship between distance x and illumination intensity, and FIG. 10 is a flow chart showing an example of the operation of the device according to the present invention. FIG. 3 is a diagram showing an example of a print according to the invention. 10...Detection head, 11, 12...Fluorescent lamp,
13...Photoelectric detector, 14...Shielding box, 15,1
6... Slit, 17... Light shielding box, 18... Partition plate, 20... Printing plate, 21... Biting, 22... Biting end, 23... Calibration mark, 24
... Non-printing area, 25... Drawing area (printing effective area),
36... rotary encoder, 38... suction device, 40... arithmetic processing unit, 41... amplifier circuit,
42...Multiplexer, 43...AD converter,
44... CPU, 45... ROM, 47... Keyboard, 48... Printer, 49... Input/output control device, 50... Reading circuit, 74... Front panel, 7
2, 73...Guide rail, 74...Stage,
75, 76...pin.

Claims (1)

[Scope of Claims] 1. A detection head having a light source that irradiates light onto a detection area of a printing plate for offset printing, and a plurality of optical sensors that receive reflected light from the detection area;
An offset device comprising: a drive means for moving the detection head relative to the printing plate; and a signal processing means for determining the picture area ratio of the printing plate using a measured value of the amount of reflected light obtained from the output signal of the optical sensor. In the device for measuring picture area ratio of a printing plate for printing, the plurality of optical sensors are aligned in the width direction with respect to the plate surface of the printing plate, and the signal processing means is configured to measure the area ratio of the printing plate according to information regarding the dimensions of the printing plate to be measured. ,
Offset printing characterized in that the pattern area ratio is determined using the measurement value of the amount of reflected light from the minimum number of sensors necessary to cover the reflected light from the detection area of the printing plate among the plurality of optical sensors. Image area ratio measurement device for printing plates.