JPS637603B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention provides a printing plate used for offset printing,
The present invention relates to an ink supply amount measuring device that measures the ratio of printed portions and non-printed portions of proofs, clean sheets, etc. printed before printing, and outputs an appropriate ink supply amount necessary for printing.

Conventionally, when measuring the ratio of printed parts and non-printed parts of printing plates, proofs, reprints, etc., the light source is applied to the object to be measured, such as the printing plate, for each divided area or the entire surface, and the light is reflected. This is done by measuring the amount of light, and the amount of ink supplied is determined based on this. However, if the overall brightness of the light source changes or the brightness distribution changes, this can become a major cause of measurement error. As a countermeasure against this problem, it is generally necessary to periodically calibrate the brightness. In addition, when installing a brightness change detector to detect brightness changes and automatically correcting the measurement results based on this, the installation location and characteristics of the brightness change detector may not match those of the ink supply amount measuring device. It is not possible to make accurate corrections. Furthermore, if the luminance distribution of the light source changes, the reflection state of the entire measurement area will naturally change, so in that case, fine corrections will be required for the entire measurement area. The surrounding reflection state changes depending on the ratio of printed and non-printed areas around the measurement area.
This results in unnecessary changes in the reflected light to the measuring device, resulting in measurement errors. It is possible to eliminate the influence of reflection around the area to be measured by providing the measuring instrument with directivity. It is possible to provide directivity using a mask plate or lens, but when using a lens, the amount of incident light decreases as it approaches the periphery of the lens from the optical axis of the lens. There were many problems such as errors in the measured values.

SUMMARY OF THE INVENTION An object of the present invention is to provide a measuring device that solves these problems and determines the amount of ink supplied based on the measurement of the ratio of printed areas to non-printed areas of printing plates, proofs, clearings, etc.

For this purpose, the ink supply amount measuring device of the present invention has the following features:
A mask case is installed in front of the measuring device to block light from outside the measuring area, and the measuring device has a lens and a plurality of photoelectric conversion element arrays, making it possible to measure the measuring area under the same conditions at all times. The output signal of the measuring device is extracted as a continuous signal train of each element, and this is converted into an analog waveform. By integrating this analog waveform, the area ratio of the printed area and the non-printed area can be calculated. It is configured to measure the ink supply amount based on this, and it is also configured to measure the ink supply amount based on the photoelectric conversion by measuring calibration plates that have the same color as the printed and non-printed areas of the object in advance. The present invention is characterized in that the measurement result of the object to be measured is corrected by equalizing the correction constant for each element of the element array.

Embodiments of the present invention will be described below with reference to the drawings.

The apparatus shown in FIGS. 1 and 2 consists of a dark box 1 which serves as a measuring section, a console 2 which performs operations, control, calculations and storage, and a printer 3 which serves as an output device. The inner surface of the dark box 1 in the measuring section is made non-reflective. An object to be measured 4 and a calibration plate 5 for correcting measured values are placed at the bottom of the dark box 1 at the same level as the measurement surface. The object to be measured 4 can be attached or removed by taking it in and out of the object setting table 6 on which it is attached. dark box 1
A traveling guide 7 is provided above, and a detection head 11 in which a measuring device 8, a light source box 9, and a mask case 10 are integrated is driven along this traveling guide 7 by a traveling driving pulse motor 12. ing.

FIG. 2 shows the detection head 11 seen from the console side in FIG. It is being As shown in FIG. 3, the mask case 10 equipped with the light source box 9 has a rectangular measurement window 10B on the bottom plate 10A.
This measurement window 10B is a measurement area S as shown in FIG.
(a×l).

Such a detection head 11 is connected to a pulse motor 1.
2, the measuring device 8 is driven stepwise along the traveling guide 7, and the measuring device 8 receives light reflected from the light source 13 on the surface of the object to be measured 4 within the measuring window 10B for each measurement area S to perform measurement. be done. To explain this measurement operation in more detail, first, the calibration plate 5 is measured to measure the reflected luminance distribution of the measurement area S, and this is stored in the console 2 as correction information. The detection head 11 is then driven by a pulse motor 12, moved to above the object to be measured 4, and then stopped. Next, measurement of the object to be measured 4 is started in the same manner, and the output from the measuring device 8 is compared with the correction information. The result is stored as a single measurement value, and the next measurement is made after the detection head 11 has traveled the distance a in FIG. 4. In this way, measurements are performed on the object to be measured 4 one after another, and over the entire area of the object to be measured. It should be noted here that the divided area handled by the ink valve in the printing device (not shown) does not coincide with the measurement area S.
Therefore, the ink supply amount must be determined for each section. For this purpose, if the width of the divided area is C as shown in FIG. The ink supply amount is determined. In other words, the output of the ink supply amount is the one measured for times c/a in FIG.
Since the detection head 11 moves as a unit with the mask case 10, light source 13, and measuring device 8, there is no change in the brightness distribution state of the measurement area when measuring the calibration plate 5 or the object to be measured 4. Stable measurement results can be obtained.

FIG. 5 shows an operational block diagram of this measuring method. The measuring device 8 includes a lens 20 and a photoelectric conversion element array 21 in which a large number of photoelectric conversion elements 1S to nS are lined up.
, an analog switch 22 for taking out the output signal of each photoelectric conversion element, a shift register 23 for selecting the analog switch 22, and a circuit 24 for controlling the shift register. When a measurement start command is issued from the central control unit 25 built in the console 2 to the measuring instrument control 26, the elements 1S, 2S...nS of the photoelectric conversion element array 21 are sequentially selected and the amount of light incident on each photoelectric conversion element is adjusted. A corresponding photoelectric conversion signal can be obtained continuously. In this way, the output waveform of the photoelectric conversion signal generated on line _l1 in FIG. 5 becomes as shown in FIG. Here, the measurement points 1P, 2P...nP in the measurement area in FIG. 4 are shown as locations corresponding to the photoelectric conversion elements 1S, 2S...nS, and the individual peak values shown in FIG. This results in a reflected light amount value of 2P...nP.

The signal shown in FIG. 6 is input to the analog waveform converter (1) 30 shown in FIG. 5, and its output waveform becomes as shown in FIG. That is, the waveform of FIG. 7 is a continuous analog waveform of the peak values of FIG. 6.
The integrator 31 converts this waveform from t ₁ as shown in equation (1).
By integrating over the time up to t _o , the amount of reflected light over the entire measurement area S in FIG. 4 is obtained.

A=∫ ^tn _t1 f(t)dt …………………(1) A: Measurement area total reflected light intensity value f(t): Waveform from t ₁ to t _o in Fig. 7 t ₁ , t _o : Scan time of all photoelectric conversion elements The problem here is that, as mentioned above, unevenness in the amount of light reflected from the measurement area surface due to unevenness in the brightness change distribution state of the measurement area S causes measurement errors. Because of this, the amount of incident light decreases as it approaches the periphery of the lens from the optical axis, and there will be an error between the measurement of the object 4 having the same amount of reflection at the optical axis of the lens 20 and the measurement at the periphery. This is what happens. Therefore, 1P of the measurement area S,
Measure in advance how the amount of reflected light of 2P...nP (Fig. 4) is distributed to the photoelectric conversion elements 1S, 2S...nS of the measuring device 8 under what light incident conditions, and calculate and store this as a correction constant. Then, before the waveform shown in FIG. 7 is integrated by the integrator 31, the corrector 32 performs correction using a correction constant.

A calibration plate 5 is provided to perform such correction, and before measuring the object to be measured 4, the calibration plate 5 is first measured to check the output states of the photoelectric conversion elements 1S, 2S, . . . nS. The calibration plate 5 for this purpose has the same length and width as the measurement area S of the measuring device 8, and is printed with two-color areas 5A and 5B of the same tone as the printed and non-printed areas of the object 4, respectively. 8, as shown in FIG. Therefore, the measurement of the calibration plate 5 is carried out twice: the area portion 5A of the printed portion and the area portion 5B of the non-printed portion. The output waveforms are shown in FIGS. 9 and 10. Here, if the color tone of the printed part of the proof plate 5 is bright,
The output waveform is as shown in FIG. 9, and if the non-printed area has a dark tone, the output waveform is as shown in FIG. 10. The two measured values on the calibration plate 5 shown in FIGS. 9 and 10 are given to the central control unit 25 through the sample hold 33 in FIG. 5, and are stored for each photoelectric conversion element 1S, 2S...nS. . Here, the output signals from the sample/hold 33 and the integrator 31 are switched by the signal selection 34, converted by the analog/digital converter 35, and input to the central control section 25.

The output VS _{1 ~} of the photoelectric conversion element 1S~nS obtained by the measurement in the area 5A of the printed part shown in FIG.
Equations (2) and (3) are obtained by subtracting VT ₁ to VTn in FIG. 10 from VSn, respectively.

VS _1〜o −VT _1〜o Va／VV _1〜o ×β＝α _1〜o ………(2) α _1〜o ×(S _1〜o −VT _1〜o )=R _1〜o … (3) R _1~o : Correction result by the corrector 32 S _1~o : Measurement output of the measured object 5 shown in Fig. 6 α _1~o : Correction constant β: Span correction constant V ₀ : Necessary as measurement span V _a : Maximum value among VV ₁ to o Here, the waveforms V _{s to o} in Fig. 9 and the waveforms VT _{1 to o} in Fig. 10 are waveforms because the measured calibration plate 5 is of a single color. The highs should flatten out. Therefore, the central control unit 25 calculates each correction constant for the photoelectric conversion elements 1S to nS using equation (2).

The span correction constant β is used to adjust the measurement span.
This is a correction constant for the overall fluctuation of the peak value in Figure 0.

V _a /VV _{1 to o} are for correcting variations in the output of individual photoelectric elements, and of course the measurement area S
It is also possible to correct unevenness in irradiation brightness.

The correction constants α _{1 to o} have a pattern as shown in FIG. Then, it is stored in the central control unit 25.

By measuring the calibration plate 5 in this way, the first
After obtaining the correction constant α _1~o as shown in Fig. 1, the detection head 11
Then, the measurement of the object 4 to be measured is started.

In this measurement, measurement signals as shown in FIG. ₇ appear sequentially on line l2 from time _t1 to _to . On the other hand, in synchronization from time _t1 to _t0 , a correction constant waveform (shown in FIG. 11) is applied to line _l3 from the central control unit 25 via a digital/analog converter 36, and analog waveform conversion (2) is performed. 37, an analog waveform with continuous peak values appears on line _l4 . At the same time, the measurement results on the non-printed part of the calibration plate 5 shown in FIG.
The signal is applied to line _l5 via analog converter 38, and by analog waveform conversion (3) 39, an analog waveform with continuous peak values appears on line _l6 . Then, the compensator 32 performs the calculation of equation (3) on these together with the measured value given by line _l2 , and the measured waveform is corrected. This output signal is t ₁
The integrator 31 integrates with a scanning time of t _o from t _o
The central control unit 25 stores the integral value up to . This completes one measurement, that is, one measurement area, and the detection head 11 travels the distance a shown in FIG. 4 and performs the next measurement in the same manner. Such measurements are repeated over the entire surface of the object to be measured 4. A time chart for this measurement is shown in FIG.

The effects of the ink supply amount measuring device according to the present invention will be explained as follows. In other words, in the past, operators had to adjust the ink valve while checking the finished print to determine whether the ink supply amount was appropriate, which resulted in a lot of wasted paper before they could adjust the appropriate ink amount. This work required considerable skill, but by using the device of the present invention, even unskilled workers can easily set the appropriate ink supply amount, and what's more, the measurement results can be checked before printing starts. By setting the ink valve, you can significantly reduce wasted paper. This is because measurement errors due to variations in the brightness of the light source, variations in photoelectric conversion element characteristics, and uneven brightness in the measurement area, which have been problems in the past, can be resolved by measuring a calibration plate and calculating an appropriate correction constant before starting measurement. This is because the problem was solved by using a so-called automatic cavration method in which the object to be measured is measured while making corrections, and as a result, highly accurate and stable results can be obtained.

Furthermore, digitizing and measuring the output of each photoelectric conversion element of a measuring instrument requires a large amount of memory.
Also, it takes a lot of time for calculations such as correction and integration, but the method of the present invention uses a method of integrating the photoelectric conversion output of the measuring instrument as an analog waveform, so it has the advantage of requiring less memory and less calculation time. be.

In addition, if the area ratio of printed matter of two colors is measured by the amount of reflected light, the color of the calibration plate should be set to the two colors.
It can be measured by color, and it goes without saying that it can be applied in many ways other than the above-mentioned device.

[Brief explanation of the drawing]

1 and 2 are an elevational view and an end view of an ink supply amount measuring device which is an embodiment of the present invention. Figure 3 is a perspective view of the mask case. FIG. 4 is a perspective view showing the measurement area by the measuring device. FIG. 5 is a block diagram of the apparatus shown in FIGS. 1 and 2. FIG. 6, FIG. 7, and FIGS. 9 to 11 are explanatory diagrams showing waveforms. FIG. 8 is a perspective view showing the calibration plate. FIG. 12 is a time chart showing the measurement. 1... Dark box, 2... Console, 4... Measured object, 5
... Calibration plate, 8... Measuring device, 9... Light source box, 10... Mask case, 11... Detection head, 12... Pulse motor, 13... Light source, 20... Lens, 21... Photoelectric conversion element array, 22... Analog switch, 23 ...Shift register, 24...Shift register control circuit, 25...Central control unit, 26...Measuring instrument control, 30, 37, 39...Analog waveform conversion, 31
...Integrator, 35, 36, 38...Converter.

Claims (1)

[Scope of Claims] 1. A mask case that has an opening that defines the measurement area of the object to be measured and that blocks light from outside the measurement area;
It has a light source that is attached to the mask case and illuminates the measurement area of the object to be measured, and a measuring device that guides reflected light from the measurement area of the object through a lens onto an array consisting of a plurality of built-in photoelectric conversion elements. a detection head formed of a dark box, a drive device for moving the detection head in steps along a dark box, and scanning the entire surface of the object by sequentially moving the measurement area, and the object to be measured. a calibration plate placed in a dark box at the same level as the object to be measured so that the printed part and the non-printed part are printed separately in the same color as the printed part and the non-printed part, and can be placed individually in the measurement area; a circuit for detecting the output signal of the photoelectric conversion element as a continuous signal train and then converting the peak value into a continuous analog waveform; A correction circuit that calculates and stores a correction constant; A correction circuit that corrects the output signal of the measuring device based on the correction constant; and A correction circuit that integrates the corrected front analog waveform to separate the printing section and the printed section. An ink supply amount measuring device comprising: a circuit for measuring an area ratio of printed parts and non-printed parts in the measurement area; and a circuit for determining an ink supply amount based on the area ratio of printed parts and non-printed parts in the measurement area.