JPS6335428B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION <Industrial Application Field> The present invention relates to a method of processing signals obtained by scanning inspection marks in printing condition inspection of multicolor sheet-fed printed matter.

<Prior art> Conventionally, the printing condition of multicolor sheet-fed printed matter has been inspected by stacking an appropriate number of printed sheet-fed printed materials and manually inspecting them by turning them over one by one, commonly known as "para-inspection." I was at a loss as to how to call it.

For this reason, conventional inspection methods are not only inefficient and unreliable, but also increase labor costs and prevent cost reductions in printed matter.

Therefore, inspection marks consisting of stripes corresponding to each printing color were placed on the corners of multicolor sheet-fed printed materials at the same time as printing, and the corner of the stacked sheet-fed printed materials was removed using several suction blades and wiper pins. When turning the inspection mark one by one, light is irradiated onto the inspection mark, an image of the mark is formed on a photoelectric element by a lens, and the photoelectric element converts the color shading of the mark into an electrical signal, which is calculated by a computer etc. for inspection. A method has been proposed for inspecting printing conditions such as off-printing and misregistration by inspecting the presence or absence and misalignment of stripes corresponding to each color of the mark.

<Problems to be Solved by the Invention> In the inspection method proposed by the applicant, methods such as detecting the stripe position by slicing the density signal obtained from the photoelectric element at an appropriate density level do not Since the position of each stripe cannot necessarily be detected accurately, it has not been possible to perform a satisfactory inspection of printed matter, which requires high inspection accuracy.

In the above method, a density signal corresponding to the shade of color of the inspection mark obtained by scanning the inspection mark with a photoelectric element is input, and this density signal is subjected to signal processing such as differentiation and slicing to perform the inspection. Provided is a signal processing method capable of accurately detecting the position of each stripe by obtaining an output signal indicating the position of the sharpest change in density between the image area and the base (non-image area) of a stripe of a mark. The purpose is to

<Means for Solving the Problems> In the printing condition inspection of multicolor sheet-fed printed matter, the present invention provides an inspection mark made of each printing color on the sheet-fed printed matter to be inspected in advance at the same time as printing, and then prints the inspection mark. An analog density signal corresponding to the density of the inspection mark is obtained by scanning with a suitable photoelectric element, and the obtained analog density signal is processed to determine the image area and base (non-image area) of the stripe of the inspection mark. A printing condition inspection of sheet-fed printed matter that obtains an output signal indicating the position of the most rapid density change, that is, a signal indicating the position of the stripe, and inspects printing conditions such as off-printing and misregistration based on the obtained output signal. In the signal processing method, the analog density signal is subjected to peak rectification to obtain a base density signal corresponding to the density of the base of the printed matter, the analog density signal is differentiated to obtain a first-order differential signal, and this first-order differential signal is used as the base density signal. A boundary portion signal is obtained by slicing based on the density signal to indicate the boundary portion moving from the image area to the base, and the first differential signal is differentiated to obtain a second differential signal, and this second differential signal is set to the zero level. A boundary point signal is obtained by slicing at , and in the presence of a pulse of the boundary portion signal, the pulse of the boundary point signal is used as a trigger to detect the most rapid position of the density change moving from the print area to the base of the inspection mark on the printed material. and inverting the base signal and slicing the first-order differential signal based on the inverted base density signal to obtain a boundary portion signal indicating a boundary portion transitioning from the base to the image area. , in the presence of the pulse of the boundary part signal, the pulse of the boundary point signal is used as a trigger to obtain an output signal indicating the most abrupt position of density change from the base of the inspection mark to the image area of the print. This is a signal processing method for inspecting the printing condition of sheet-fed printed matter.

If printing conditions such as off-printing and misregistration are inspected based on the output signal that accurately indicates the position of the sharpest density change between the base of the inspection mark and the print area, the printing condition of the printed matter can be inspected. This is a signal processing method that can be made more accurate.

According to the present invention, it is possible to obtain an output signal that accurately indicates the position of the sharpest density change between the print area and the base (non-print area) of the stripe of the inspection mark. Inspection equipment e.g.
If applied to a printing condition inspection device such as that disclosed in USP. 3915090, the position of the inspection stripe will be able to be detected more accurately.

<Operation> Since the boundary portion signal is obtained by slicing the first-order differential signal based on the base density signal, it is a pulse signal that indicates the boundary portion between the image area and the base. There is a pulse at the point where the density change between the image area and the base is most rapid, that is, a boundary point, approximately at the center of the image, and where there is no noise, that is, there is a boundary point, there is a pulse, and there is no boundary point. The point is that no pulses occur anywhere.

In addition, since the boundary point signal is obtained by slicing the second-order differential signal at the 0 level, it is a pulse signal where the pulse ends or begins at the position where the density change between the image area and the base is most rapid. teeth,
Although it contains noise (there are end points and start points of the pulse other than the boundary points), there are points near the boundary points that do not contain noise.

Therefore, by combining this boundary portion signal and the boundary point signal, the noise in the boundary point signal is removed and the position (boundary point) where the density change is the sharpest between the print area and the base of the inspection mark on the printed material is determined. It is possible to obtain an output signal containing only

<Example> Hereinafter, the present invention will be described in detail with reference to an example shown in the accompanying drawings.

In Fig. 1, 1 is a multicolor sheet-fed printed matter, and its corners are marked with stripes 2, 3, 4, and 5 of each color used in printing, and a triangular pattern 6 of the same color as stripe 1 of the first color. An inspection mark is provided. Two stripes 2, 3, 4, and 5 are provided perpendicularly to the scanning line S at appropriate intervals for each printing color. 7 is a suction blade of number N (see Fig. 6),
The flat blade surface 7a is provided opposite to the lower side of the corner provided with the mark M of the multicolor sheet-fed printed matter 1, which is stacked with the corners provided with the mark M aligned.
is caused to undergo repetitive rotational movements by a shaft 7b which is pivotally connected to the machine N. Reference numeral 8 denotes a wiper pin of the same number N which is parallel to the suction blade 7, and continuously rotates in the direction of the arrow around the suction blade 7 eccentrically with respect to the shaft 8b by means of a flange portion 8a.

The suction blade 7 has a suction hole 9 communicating with a vacuum system (not shown) on a blade surface 7 in contact with a corner of the sheet-fed printed matter 1.
It is perforated in a. Then, as shown in FIGS. 2 to 4, the suction blade 7 adsorbs the sheet-fed printed matter 1 one by one onto the blade surface 7a through the suction hole 9. In particular, as shown in FIG. 7 rotates clockwise to direct the mark M provided at the corner of the sheet-fed printed matter 1 toward the density signal generator 10, which includes a lens and a photoelectric element. The photoelectric element (image sensor in this embodiment) of the density signal generator 10 scans the inspection marks M consisting of stripes 2, 3, 4, 5, etc. provided at the corners of the sheet-fed printed matter 1, and detects the stripes 2, 3, 4. ,5
A density signal of color shading, that is, a one-dimensional video signal is output. A strobe light source 11 illuminates the inspection mark M in synchronization with scanning. The concentration signal from the concentration signal generator 10 is:
Pulse signals are transmitted to the density signal processor 12 and analyzed there to indicate the positions of the stripes 2, 3, 4, and 5, that is, the starting boundary and the ending boundary of the image area of each stripe. is converted to Then, a computer calculates whether the number of pulses for each color of stripes 2, 3, 4, and 5 corresponds to the number of stripes to check for off-printing. Printing misalignment is checked by calculating whether the position of each color stripe is within an allowable range.

FIG. 7 shows a block diagram showing the details of the density signal processor 12, and 13 is a sample and hold circuit which samples and holds the density signal A from the image sensor of the density signal generator 10 to calculate the density of the envelope waveform. Convert to signal B (analog signal). 14 is a first-order differential circuit that differentiates the density signal B and converts it into a first-order differential signal. Reference numeral 15 denotes a second-order differential circuit which further differentiates the first-order differential signal C and converts it into a second-order differential signal D. Reference numeral 16 denotes a peak rectifier circuit which rectifies the peak value of the density signal B and converts it into a peak rectified waveform signal, that is, a base density signal E indicating the density of the base (non-print area) of the printed material. Reference numeral 17 denotes a positive side comparator circuit which receives the above-mentioned first-order differential signal C and base density signal E and slices only the plus-side signal of the first-order differential signal C to slice the boundary portion from the image area of the stripe to the base. A boundary portion signal F is obtained.
Reference numeral 18 denotes a signal inverting circuit, which obtains a base density signal G by inverting the base density signal E. Reference numeral 19 denotes a negative side comparator circuit which receives the above-mentioned first-order differential signal C and a signal G obtained by inverting the base density signal, and slices only the negative-side signal of the first-order differential signal C from the base to the image area of the stripe. A boundary portion signal H indicating the portion of the boundary to be moved is obtained. 20 is a slicing circuit which slices the second-order differential signal D at zero level to indicate the peak of the waveform with the steepest change of the first-order differential signal; in other words, it indicates the peak of the waveform with the steepest change from the image area to the base or from the base to the image. A boundary point signal I is obtained that includes a pulse where the pulse ends or begins at the point of the steepest change in transition to the line portion. 21 is a one-shot multi-vibrator circuit, which is connected to the above-mentioned positive side comparator circuit 1.
7, the boundary part signal F is the primary input, and the boundary point signal I
is used as a secondary input to obtain an output pulse signal whose rising edge is at the position of each positive peak of the first-order differential signal C, that is, a pulse signal J indicating the sharpest point of density change from the image area to the base. In other words,
The one-shot multivibrator circuit 21 generates the boundary point signal I in the presence of pulses of the boundary portion signal F.
When the end point of the pulse exists, the end point of the pulse is used as a trigger to output a pulse with a constant width to obtain a pulse signal J. 22 is a signal inversion circuit,
A boundary point signal K is obtained by inverting the boundary point signal I. 23 is a one-shot multivibrator circuit, which is connected to the above-mentioned negative side comparator circuit 19.
The boundary portion signal H is used as a primary input, and the inverted boundary point signal K of the boundary point signal I is used as a secondary input, and an output pulse signal whose rising edge is the position of each negative peak of the first-order differential signal C, that is, an image from the base. A pulse signal L is obtained that indicates the point where the concentration change is most rapid toward the line portion. In other words, when the end point of the pulse of the boundary point signal K exists in the presence of the pulse of the boundary portion signal H, the one shot multivibrator circuit 23 outputs a pulse of a constant width using the end point of the pulse as a trigger. Obtain pulse signal L. 24 and 28 are shift registers which input the output pulse signals J and L and shift register the output pulse signals J and L using the clock pulse from the clock pulse generator 26 as a shift pulse. 27 and 25 are latch circuits that input the outputs of the shift registers 24 and 28 and clock pulses, and send the output pulse signals to the computer 2.
Input to 9. 30 is a concentration signal generator 10
The drive circuit receives the clock pulses from the clock pulse generator as input.

By inputting the pulse signals J and L to the first-stage computer 29, the computer determines whether there are pulses corresponding to each color as described above, the interval between the pulses of each other color relative to the pulse of the first color, and whether this is within the allowable range. Calculate whether or not the printed material 1 is unprinted, misalignment of printing, etc., and display this on the display section 41 provided in the inspection control section 40 to detect unprinting or misprinting.
It displays printed matter with misaligned prints.

The inspection control unit 40 includes the signal processor 1 as described above.
2. A computer 29, a display section 41, a control mechanism for the entire device, a control panel, etc. are provided.

FIG. 8 shows details of each of the above-mentioned signals A to L.

The reason why each of the above circuits is used to process the concentration signal from the concentration signal generator 10 will be described below. To explain the density signal A obtained by the density signal generator 10 to explain this, FIG. 9 is an explanatory diagram showing the magnitude of the scanning width of the photoelectric element, and FIG. 9A shows a narrow width photoelectric element. FIG. 9B shows an example using a scanning width Sb of a wide photoelectric element (image sensor).
Further, 2' indicates a stripe 2 of inspection marks imaged on the photoelectric element surface.

When the stripes of each color of the inspection mark M are viewed microscopically, the boundary line between the base and the image area (for example, stripe 2) is uneven, as shown in the figure, and there are also small white spots 31, dirt 32, or chips 33. , smudges 34, etc., but if they are picked up, even non-defective products may be treated as defective, resulting in inconvenient results.

Therefore, it is necessary to reduce the noise caused by these as much as possible. Stripe 2 with narrow scanning width Sa
When scanning with a wide scanning width Sb, when the chip 33 etc. enters the scanning width, it will be caught as if the boundary point is shifted, but if scanning with a wide scanning width Sb, the chip 33 etc. will occupy the entire scanning width. The proportion of
Therefore, the noise caused by these factors is reduced, and scanning with a photoelectric element having a wide scanning width Sb enables more accurate inspection. Significant noise reduction was observed in this example by using a 17 mil scan width photoelectric element.

A density signal processor 12 is used to extract necessary output pulse signals from the density signal A from the density signal generator 10, that is, signals J and L that accurately indicate the positions of both ends of each stripe.
That is, the density signal processor 12 is composed of the above-mentioned circuits in order to recognize the point where the level change of the density signal A, which is the signal indicating the position of each stripe, is most rapid as the boundary between the printing paper and each stripe.
To explain this in more detail, in order to obtain an output pulse that shows only the most rapid level change of the concentration signal A, the concentration signal A is sent to the sample and hold circuit.
Sample and hold is carried out at step 3, and the output density signal B of the envelope waveform is differentiated to obtain a first-order differential signal C. When this signal C is sliced by comparators 17 and 19, the density signal B is subjected to peak rectification in order to automatically correct variations in the flash of the strobe light source 11, changes due to the color of printing paper, and lens aberrations. The base density signal E thus obtained is taken as the slice level. However, since it is not possible to capture the most rapid peak of level change, that is, the boundary point, only with the boundary portion signal F obtained by slicing the first-order differential signal C, the second-order differential signal D, which is obtained by further differentiating the first-order differential signal C, is used. Obtain the boundary point signal I sliced at zero level, and use this signal I as a trigger pulse to operate the one-shot multivibrator 2.
1 and 23 are activated to obtain output pulse signals J and L of a constant width whose rise is at the peak value of the first-order differential signal C, that is, at the point where the concentration change of the concentration signal is most rapid. It has been confirmed that by using this output pulse signal as the boundary point between the printing paper and each stripe, extremely highly accurate inspection becomes possible. Inspection of the positions of the stripes 2, 3, 4, and 5, which serve as inspection marks, is not based on the spacing between each other, but on the absolute distance from the first stripe (2 in this example). shall be. This is because the printing corresponding to the color of the first stripe is used as a reference for checking for misregistration.
This is because if the distance from the second to fourth stripes is equal to the specified value, it can be determined that there is no misregistration.

FIG. 10 shows a flowchart of the test performed by the computer 29, and the test is performed in the following manner.

The process starts at 802, clears the previous data at 804, checks whether there is a start signal from aircraft N at 806, and proceeds to 810 if there is a start signal. At 810, the correct reference value of the item to be inspected is input, and at 812, the presence or absence of a termination signal from the number of aircraft N is checked. If there is, the comprehensive result is displayed at 830, and the process returns to 806. If there is no end signal, mark data of the object to be inspected is input in 814, and a deprinting inspection is performed in 816. If there is no deprinting, a misregistration check is performed in 818. If there is no misregistration, the process returns to 810. If it is determined at 816 or 818 that there is an off-print or a misregistration, the process proceeds to 832, where it is displayed on the display, stored, and notified with a buzzer (not shown), and a signal is sent to the number machine N. A border paper indicating the position is inserted between the prints.

In addition, in the above embodiment, the case was described in which the stripes serving as inspection marks were of four colors, but this number is increased or decreased depending on the number of printing colors, and each stripe is two for each color. However, this is because the inspection data is obtained for four points for each color, and this can be increased or decreased as desired.

Furthermore, the present invention is not limited to the above-mentioned embodiments; for example, since the polarity of a signal, such as plus or minus, is determined by the type of circuit element used, the inverting circuit may be You can design it as appropriate, such as by including .

<Effects of the Invention> As described above, according to the method of the present invention, when the number of sheets of multicolor printed matter is separated by a counting machine, light is irradiated to the inspection mark provided at the corner of the multicolor sheet-fed printed matter, and the inspection mark is In a method for inspecting the printing condition of a multicolor sheet-fed printed matter based on the density signal of the inspection mark from the photoelectric element by scanning with a photoelectric element, there is a change in the density between the print area of the inspection mark and the base of the density signal. can output the most abrupt position completely and accurately. Therefore, it is possible to inspect multicolor sheet-fed printed matter for deprinting and misregistration with extremely high precision and reliability using a computer or the like.

[Brief explanation of the drawing]

The drawings show one embodiment of the invention.
The figure is a perspective view showing the correspondence between the sheet-fed printed matter and the suction blade, FIGS. 2 to 4 are explanatory views showing the operation of the suction blade, and FIG. 5 is an explanatory view showing the scanning system of inspection marks. Figure 6 is a perspective view of the main parts of the machine, Figure 7 is a block diagram of the signal processor, Figure 8 is a signal diagram showing the output signals of each circuit shown in blocks in Figure 7, and Figure 9A. , B is an explanatory diagram showing the relationship between two types of scanning widths, narrow (FIG. 9A) and wide (FIG. 9B) for a striped image, and FIG. 10 is a flowchart of the computer software used in this invention. . Explanation of the symbols in the figure, 1... sheet-fed printed matter, 2 to 5... stripe, 7... suction blade,
8... Wiper pin, N... Number of members, 10... Concentration signal generator, 12... Concentration signal processor, 13...
...Sample hold circuit, 14...First order differential circuit, 15...Second order differential circuit, 16...Peak rectifier circuit, 17,19...Comparator circuit, 18,
22... Signal inversion circuit, 20... Slice circuit,
21, 23...One-shot multivibrator circuit.

Claims (1)

[Claims] 1. An inspection mark consisting of stripes of each printing color on a multicolor sheet-fed printed matter is scanned with a photoelectric element to obtain an analog density signal corresponding to the density of the inspection mark, and the obtained analog density signal is used as a signal. By processing, an output signal is obtained that indicates the position of the sharpest density change between the print area and the base (non-print area) of the stripe of the inspection mark, and based on the obtained output signal, deprinting and misregistration are detected. In a signal processing method in a printing condition inspection of a sheet-fed printed matter, the analog density signal is subjected to peak rectification to obtain a base density signal corresponding to the base density of the printed matter;
The analog density signal is differentiated to obtain a first-order differential signal, and this first-order differential signal is sliced based on the base density signal to obtain a boundary portion signal indicating a boundary portion transitioning from the image area to the base; A second differential signal is obtained by differentiating the differential signal, a boundary point signal is obtained by slicing this second differential signal at the zero level, and a pulse of the boundary point signal is obtained in the presence of the pulse of the boundary portion signal. As a trigger, an output signal indicating the most rapid change in density from the print area to the base of the inspection mark on the printed matter is obtained, and the base density signal is inverted, and the first differential signal is converted into the inverted base density signal. Based on the slice, a boundary part signal indicating the boundary part transitioning from the base to the print area is obtained, and in the presence of the pulse of this boundary part signal, the pulse of the boundary point signal is used as a trigger to slice the base of the inspection mark on the printed material. 1. A signal processing method for inspecting the printing condition of sheet-fed printed matter, characterized by obtaining an output signal indicating the position of the sharpest change in density from the to the printed area.