JPH0123818B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for inspecting running printed matter, and more particularly to a method for correcting pixel reference density values used for inspection in accordance with changes in running speed of printed matter.

In order to inspect objects having density information such as printed matter, a method is adopted in which reference data and detection data are digitally compared and determined for each pixel. In this method, when the printed material is running, detection data is obtained by sequentially scanning an image sensor arranged perpendicular to the running direction of the printed material, as shown in FIG.

In this case, the detection data actually taken out by the image sensor is taken out along the direction A, which is a combination of the traveling direction x of the printed material and the scanning direction y of the image sensor.

Here, when the running speed of the printed matter changes, the direction A from which the detected data is taken changes as shown in FIGS. 2a and 2b. In other words, assuming that the scanning speed of the image sensor is constant and the running speed of the printed matter, that is, the relative running speed between the printed matter and the image sensor increases, the actual scanning direction of the image sensor changes from A in Figure 2a to B in Figure 2b. Changes to

As a result, when looking at the one-pixel detection areas C and D of the image sensor shown in Figures 2a and b, in the case of Figure 2a, the entire area detects black pattern data, whereas the second In the case of FIG. b, white pattern data is included in part of the area. This indicates that the amount of light reaching the image sensor changes as the running speed of the printed matter changes. This tendency is particularly noticeable at measurement positions where the concentration changes significantly.

The present invention has been made in view of the above-mentioned points, and provides a method for inspecting printed matter by taking into account travel speed information of the printed matter.

Embodiments of the present invention will be described below with reference to FIGS. 3 to 7.

FIG. 3 shows a data importing section in an inspection apparatus for running printed matter, which is the object of the present invention. In this figure, the printed matter P is fed in the x direction along the rotation direction of the rotary drum Q. Then, the image sensor camera 1 detects the printed matter P along the longitudinal direction of the rotating drum Q, that is, the direction y perpendicular to the traveling direction x.
, and the density information of each pixel obtained thereby is digitally converted by the A/D converter 2 and provided to the memory. The memory includes a reference value memory 3 and a detected value memory 4. When the switch SW is moved to the solid line position shown in the figure, data is written to the reference value memory 3, and when the switch SW is moved to the broken line position shown, data is written to the detected value memory 4.

FIG. 4 shows the recorded contents of the reference value memory and the detected value memory. In both memories, density information is written at addresses determined by the printing width direction division and the running direction division. Then, by reading and comparing the density information of the corresponding addresses in both memories, it is possible to determine the quality of the printed matter to be inspected.

FIG. 5 shows the configuration of an apparatus for carrying out the method of the present invention, and the same reference numerals 1 to 4 as in FIG. 3 indicate the same elements. 5 is a rotary encoder;
It is attached to a drive system for running printed matter, such as the rotating shaft of a rotating drum, and generates a predetermined number of pulses, for example 500, per rotation of the rotating drum. Therefore, by measuring this pulse for a predetermined period of time, the speed of the rotating drum can be determined. This speed information is stored when writing the reference value data, is compared with the speed information when writing the test value data, and is used to rewrite the reference value data when the difference exceeds a predetermined value. Ru. Thereby, the reference value data can be rewritten in accordance with changes in the running speed of the printed matter, and the reference value data and the inspection value data can be made under the same conditions.

Rotary encoder 5 used in this way
The speed information is sent to the internal bus BUS via the speed signal input circuit 6 and given to the reference value rewrite signal generation circuit 7.

Other elements of the apparatus shown in FIG. 5 include a scanning direction signal input circuit 8 from the image sensor camera 1;
, an arithmetic unit 9 for comparing inspection value data with reference value data and determining pass/fail, a computer 11 having an interface 10 and controlling the entire device, and an address generation circuit 12 connected to an internal bus.
Connected to BUS. The computer 11 is a so-called personal computer.
It has a CPU, memory MEM, keyboard KB and display CRT.

FIG. 6 shows the internal configuration of the reference value memory rewrite signal generation circuit 7 in FIG. , j, AND gate k, l, m, inverter n
and a decoder o.

This circuit 7 connects S1 to S via an internal bus BUS.
6 is applied to output a rewrite signal 9 when necessary.

The signal S1 is a control command given from the computer 11, and one of four operating modes is selected according to this control command S1. The four operating modes are: (1) Stop mode (hereinafter simply referred to as stop) (2) Setting mode (hereinafter simply referred to as setting) (3) Reference value writing mode
(hereinafter simply referred to as reference value) (4) Inspection mode (hereinafter simply referred to as inspection).

Signal S2 outputs the speed tolerance value (16 bits) input from the computer to ports b and c of the microcomputer MC.
Signal S3 is the speed tolerance value input from the computer and is a signal obtained by dividing 16 bits into time-division 8 bits each. Signal S4 is the speed tolerance value of 16 bits input to port B in 8 bits each. , c to the AND gates k, l and inverter n to control the latches g, h for input to the circuit 7. The signal S5 is the board selection signal given by the computer when setting the speed tolerance to this circuit 7. The signal S6 is a pulse train signal as speed information from the rotary encoder 5, and these are given via the internal bus BUS.

On the other hand, signals S7 and S8 are internal signals. Signal S7 is a signal given to counters i and j from microcomputer MC for initializing counters i and j that count pulses from rotary encoder 5. Signal S8 is This is a signal given from microcomputer MC to AND gate m to determine the counting time of counters i and j.

The signal S9 is a signal applied to the internal bus BUS from the reference value memory rewrite signal generation circuit 7, and is a reference value memory rewrite signal that is output when the set allowable speed is exceeded.

FIG. 7 is a flowchart showing the operation of the reference value memory rewrite signal generation circuit 7 shown in FIG.
Explain the operation.

Now the signal S1 is sent to the circuit 7 through the internal bus BUS.
.about.S6 is given, the microcomputer MC first reads the contents of the control command S1. In the case of "stop" or "setting" mode, reading of the control command S1 is repeated. however,
In the "setting" mode, when the board selection signal S5 from the computer 11 selects the board of this circuit 7, ports b and c in the microcomputer MC are sent via latches g and h in response to the write signal S2. A speed tolerance value S3 is written.

When the control command S1 is in the "reference" mode, the microcomputer MC outputs the signal S7 to reset the counters i and j, resets the counters i and j, and then sends the count start signal S8 to the AND gate m. give rotary encoder 5
Takes in pulses from

Microcomputer MC measures a predetermined time.

The microcomputer MC outputs a count end signal S8 to the counters i and j, and the reception of pulses from the rotary encoder 5 is completed.

Input the counted values of counters i and j to the microcomputer MC via ports d and e, and input them to the microcomputer MC.
It is stored in a register in the MC as the traveling speed information at the time of importing the reference value data.

Return to reading of control command S1.

When the control command S1 is in the "inspection" mode, the speed tolerance values input to ports b and c during the "setting" mode are transferred to the register in the microcomputer MC.

Pulses are taken in from the rotary encoder 5 in the same way as in the "reference" mode.

The absolute value of the difference between the traveling speed information at the time of importing the test value data and that at the time of importing the reference value data is determined.

If the absolute value of this difference is greater than or equal to a predetermined value in terms of the speed tolerance, a reference value memory rewrite signal S9 is output to the internal bus BUS.

For example, suppose that the first to (n-1)th printed matter is inspected normally, and the running speed of the printed matter changes during the inspection of the nth printed matter. In this case, a rewrite signal is generated immediately, and the next test (n+
1) Control command s1 (sixth
The reference value write mode is given to (Fig.). As a result, in FIG. 3, the density information of each pixel in the (n+1)th printed matter given from the camera 1 is rewritten into the reference value memory 3.
written to. Then, the speed at that time is stored in a register in the microcomputer as a reference value speed.

After rewriting the speed information in this way, the process moves to the inspection of the (n+2)th sheet in response to the control command s1.

Return to reading of control command S1.

As described above, the present invention compares the speed information at the time of importing the test value data of the running printed material to be inspected with the speed information at the time of importing the reference value data stored in advance, and when the difference exceeds a predetermined value, Since the reference value data is rewritten using the data from the running printed matter after the speed change as new reference value data, it is possible to prevent erroneous judgments in running printed matter inspection due to differences in running speed.

[Brief explanation of drawings]

Fig. 1 is a diagram showing the actual scanning direction when a running printed matter is scanned in the width direction, and Fig. 2 a and b are diagrams showing changes in detection contents due to changes in the running speed of the printed matter. , FIG. 3 is a diagram showing the configuration of the data acquisition section of the traveling printed matter inspection apparatus to which the present invention is applied, FIG. 4 is a diagram explaining the storage contents of the two memories in the configuration of FIG. 3, and FIG. FIG. 6 is a diagram showing the configuration of a reference value memory rewrite signal generation circuit in the device of FIG. 5, and FIG. 7 is an operation of the circuit of FIG. 6. This is a flowchart showing the following. 1... Image sensor camera, 3, 4... Memory. MC...Microcomputer, a~f...Microcomputer MC
port, g, h...latch, k, l, m...and gate, n...inverter, o...decoder, BUS...internal bus, S1...control command,
S2...Write signal, S3...Speed tolerance, S4
...Latch selection signal, S5 ... Board selection signal, S
6... Speed information, S7... Counter set, reset signal, S8... Counter start counting,
End signal, S9...Reference memory rewrite signal.

Claims (1)

[Scope of Claims] 1. A method for inspecting running printed matter in which test value data taken out from running printed matter is compared with reference value data previously taken out and written from running printed matter to determine pass/fail, comprising: At the time of importing data, print travel speed information is imported, and this print speed information is successively compared with the print speed information imported at the time of importing the inspection value data, and when the speed difference exceeds a predetermined value, the print speed is A method for inspecting running printed matter, characterized in that data from the running printed matter after the change is rewritten as new reference value data.