JPH0539889Y2 - - Google Patents

Description

[Detailed Description of the Invention] [Technical Field] The present invention relates to a system for checking the printing condition of printed matter and managing the print quality.

[Prior art and its problems]

As a system for managing the print quality of printed matter,
2. Description of the Related Art Conventionally, a so-called density management system has been known that measures the density of a printing scale applied to a printed matter in a proof printing and manages printing quality based on the measured density.

However, conventionally known density control systems can only determine the density level value for each printed sheet, and do not control halftone reproducibility or gradation reproduction, which are considered to be major factors in the quality or stability of printed materials. It is possible to know only the management data of each printed matter separately, and there is no relationship between the previous and succeeding printed matter, and the behavior of print quality over time is important for quality control. However, it was very difficult to understand.

[Purpose of invention]

Therefore, the purpose of the present invention is to provide an apparatus that can obtain not only density data but also other data representing print quality and make more accurate judgments about the quality of printed matter. Another object of the present invention is to provide an apparatus that allows the temporal transition of print quality data to be easily read, allows the trend of printing conditions to be known, and enables more efficient quality control.

[Summary of the idea]

The present invention, which was developed to achieve the above object, is a quality control device for printed matter that measures the density of printed matter with the same pattern printed on multiple sheets. A density measuring means for measuring the density of a control scale having a density measuring means, and quality control data including halftone dot conversion percentage from the density of at least 100% solid area and intermediate gradation area among the densities measured for each printed matter. This is a quality control device for printed matter, comprising a calculation means and an output means for graphically displaying the quality control data including the halftone dot conversion percentage and the density measured for each printed matter in time series.

[Details of the idea]

The present invention will be described in detail below based on embodiments shown in the drawings.

FIG. 1 is a block diagram of the printed matter quality control apparatus of the present invention. A known reflection densitometer can be used as the densitometer 4, which measures the density of the 100% solid portion and the intermediate gradation portion of the control scale printed on the margin of the printed matter. The measured concentration data is taken into the microcomputer via the interface 9 and subjected to arithmetic processing to be described later. The microcomputer has CPU1, ROM2,
It is composed of a RAM 3 and the like, and the calculation results are stored in a floppy disk 8 by a floppy disk drive 7, and outputted to a printer 5 and a plotter 6 via an interface 10.

The CPU 1 executes the program shown in the flowchart of FIG. 2, and processes the density data taken in for each printed matter.

As mentioned above, the density data input from the densitometer is input from multiple locations on one printed sheet, and the intermediate gradation areas are converted into halftone dots (for example, using the Murray-Davis formula [halftone conversion percentage = 1-10/1- 10−D _R −D _V D _V : Solid density, D _R : Halftone density]) Find the halftone reproducibility.

Next, in order to make it easier to understand the changes over time in each density data for each color and the calculated dot conversion percentage, a plotter is used to sequentially plot the data in a graph as shown in FIG. 3.

FIG. 3 is a graph for one color among Y, M, C, and BK, and actually graphs for four colors are shown at the same time, but the other three colors are omitted.

The upper graph is a graph of the density data of the 100% solid halftone area, and the middle graph is a graph of the density data of the halftone area. In both cases, the vertical axis is the density, and the horizontal axis is the number of prints (i.e., time). ). Further, the lower row is a graph of the halftone conversion percentage of the determined halftone portion, with the vertical axis representing the halftone conversion percentage and the horizontal axis representing the number of printed matter.

This represents changes over time in density data and halftone dot percentages at the same location on sequentially printed materials.

Once all the target printed matter has been processed as described above, each density step, maximum value, minimum value, average value, standard deviation, total number of samples, percentage of samples within the allowable range, etc. are recorded for each density step. Find the maximum, minimum value, average value, standard deviation, total number of samples, and the halftone conversion percentage.
Furthermore, the maximum, minimum, average, standard deviation, etc. of the halftone dot reproducibility (=actual halftone dot area (halftone dot conversion percentage)/ideal (positive) halftone dot area, etc.) are similarly tabulated and output for each color.

In the above embodiment, the dot conversion percentage (dot gain) of the intermediate gradation area may be used as data representing print quality other than the density data. In that case, calculate dot gain = (halftone dot conversion percentage) - ideal (positive) halftone dot area],
In addition to the above output, it is also possible to calculate the K value using the halftone conversion percentage and output the change in gradation reproducibility over time, or to calculate the contour reproducibility and output it in the same way. You can also do so.

[Effect of idea]

As described above, in the present invention, data other than concentration data is obtained for quality control, so more accurate control is possible. In addition, instead of using one set of quality control data for each printed sheet, we also record changes in halftone dot reproducibility over time (or number of sheets) on the spot so that it can be easily compared with previous and subsequent printed materials on the production line. This allows for faster detection of abnormal conditions, saving inspection time and reducing defective products (reducing costs). Furthermore, in addition to controlling the quality of printed matter, it is also easy to quickly detect and respond to densitometer abnormalities and printing machine abnormalities (blanket deterioration, water bar abnormalities, ink abnormalities, etc.) by long-term aggregation and comparison of before and after data. This will also help prevent quality accidents.

[Brief explanation of the drawing]

FIG. 1 is a block diagram of the quality control apparatus according to the present invention, FIG. 2 is a flowchart of arithmetic processing in a microcomputer, and FIG. 3 is an explanatory diagram showing an example of output display of the arithmetic processing results. 4...densitometer, 6...protsuta.

Claims (1)

[Utility Model Claims] A quality control device for printed products that measures the density of multiple printed products of the same pattern, comprising: density measurement means that measures the density of a control scale having 100% solid parts and half-tone parts printed on each printed product; calculation means that determines quality control data including a halftone dot conversion percentage from the densities of at least the 100% solid parts and the half-tone parts out of the densities measured for each printed product; and output means that displays in a chronological graph the quality control data including the halftone dot conversion percentage and the densities measured for each printed product.