JPS5973758A - Method and apparatus for inspecting picture pattern of printed matter - Google Patents

Abstract

PURPOSE:To enable the certain detection of many kinds of various defects to enhance inspection accuracy, by a method wherein plurality of combinations each of which is a combination of gradation difference tolerant value of a reference picture element and a specimen picture element and the tolerant value of the number of defect picture elements each exceeding said tolerant value are set and it is judged that the defect is present in the picture pattern when the defect is detected by either one of said combinations. CONSTITUTION:Each of judge elements JE1-JEn has a gradation difference tolerant value and a defect tolerance value set thereto and the values thereof are different at every each element. For example, JE1 is set so as to enlarge the gradation difference tolerant value and to reduce the defect tolerance value and constituted so as to detect spot like stain while JEn is contrarily set so as to reduce the gradation difference tolerant value and to enlarge the defect tolerance number and constituted so as to detect fine color tone difference over the entire surface of a picture pattern. In addition, JE2-JEn-1 are set so as to reside between JE1-JEn. By this constitution, JE1 and JEn detect defect with properties of both extremes of the picture pattern defects while JE2-JEn-1 detect defects with intermediate properties. When even either one of these judge elements JE1-JEn generates output showing spoilage, a spoilage signal is outputted from an OR gate OR.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method and apparatus for inspecting patterns on printed matter.

As shown in FIG. 1, the conventional printed matter pattern inspection device scans the printed matter 1 in the width direction with a line sensor camera 2 and extracts image density information based on a reflection device. By synchronizing the scanning of the camera 2 with the output of the encoder 4, the sample pattern 5 is
(Fig. 2) is divided into a large number of small pixels in a matrix.

The density of each of these pixels is sequentially compared with the corresponding small pixels of the sample pattern 6 (FIG. 2), which has been similarly divided and recorded in the memory, to detect the presence or absence of a defect.

Here, when inspecting the pattern of printed matter, it is necessary to set a certain tolerance value in order to avoid misjudging normal paper as horizontal paper. This is necessary because there is some variation in density etc. even on regular paper, the printing position is not always in the same position in a strict sense, and the presence of noise is unavoidable. An appropriate tolerance value is given to the gradation difference in the amount of reflected light between the pixel and the sample pixel.

This tolerance value varies depending on the number of pixels depending on the picture, and its -
Examples include: In other words, for pixels near the edges of a picture, the above-mentioned gradation difference becomes thicker due to positional deviation of the print conveyance system, so a larger tolerance is given (Japanese Patent Application No. 179599/1982).
Since the gradation difference due to positional deviation is small in flat parts of the image, it is necessary to give the pixels in such parts a tolerance value that does not misjudge original paper as waste paper due to variations in original paper or noise. good. Therefore, a defect tolerance number is set for the total number of defective pixels that exceed the prescribed tolerance value, and paper is judged as waste or good paper depending on whether the number of defective pixels exceeds the tolerance value. . In other words, this method inspects a pattern based on a combination of the allowable number of defects and the allowable gradation difference value given to each pixel.

The relationship between the allowable number of defects and the allowable gradation difference determination level (%) given to each pixel can be expressed by the characteristic shown in FIG. 3, and this characteristic shows the following. That is, in order to detect spot-like, high-contrast stains caused by ink splatter among various defects, for example, the acceptable judgment level must be set to a high value, and the acceptable number of defects must be small. Furthermore, in order to detect subtle color tone defects over the entire image caused by poor color matching, it is necessary to set the gradation difference tolerance value small and the defect tolerance number large. The shaded area above the characteristic curve in Figure 3 is the setting range that can be inspected, and the non-shaded area below the curve is the setting range where normal paper is incorrectly judged as horizontal paper. It is necessary to set an area closer to the lower right, and in cases of poor color matching, it is necessary to set an area closer to the upper left.

However, since conventional printed matter pattern inspection equipment inspects using only one combination of gradation difference tolerance and defect tolerance, the characteristics of the pattern defects that can be detected are fixed, making it difficult to handle a wide variety of pattern defects. I can't. As a countermeasure for this, it is necessary to provide a separate defect extraction device, which leads to an increase in the size and complexity of the device. The present invention has been made in consideration of the above points, and the To provide a method and apparatus for detecting pattern defects in printed matter that can deal with various pattern defects by setting a combination of a tolerance value for gradation and a tolerance value for the number of defective pixels exceeding this tolerance value. It is something.

An embodiment of the present invention will be described below with reference to FIGS. 4 to 8.

FIG. 4 shows the overall configuration of a printed matter pattern inspection apparatus according to the present invention. In this device.

A pattern on a printed matter 1 is moved by a camera 2 and image information is taken out. At this time, the rotation amount of the conveyance system cylinder 3 is taken out by the rotary encoder 4 and given to the synchronization circuit 7. The synchronization circuit 7 is connected to the camera 2. The output is applied to an A/D converter 8 and an address circuit 9 to perform synchronization of the camera 20, conversion synchronization of the image information taken out by the camera 2, and address assignment of the memory 11. A
The switch sw inserted on the output side of the /D converter 8 is k
A circuit 10 for determining whether to give the output of the converter 8 to the memory 11
When the camera 2 is extracting image information from the specimen print, the switch SW
When the camera 2 is taking out the image information from the sample print, turn the switch SW toward the solid line side to provide the image information (hereinafter referred to as sample data) to the memory 11. data) is supplied to the determination circuit 10 and compared with the sample data read out from the memory 11 at the same time to detect pattern defects. Judgment (
b) Among the two input signals of path 10, S indicates sample data and T indicates sample data, respectively.

FIG. 5 shows the internal configuration of the determination circuit 10 in the device shown in FIG. 4, in which n determination elements JE1
．． JE2...t by JEXl and OR gate OR
S has been completed. Each judgment Niremen) JEl, JE2
...JEn is given sample data S and sample data T, and the outputs J□, J2...Jll are OR)
The output TJ of (or game) OR becomes the overall judgment signal.

Each determination element has a gradation difference tolerance and a tolerance number of defects set, and the values differ for each element. For example, JE technology has a large gradation difference tolerance and a small number of defects to detect spot stains, while JEn, on the other hand, has a small gradation difference tolerance and a large number of defects. (This is set to detect subtle tonal differences over the entire image.And JE
2 to JEn-□ are intermediate settings between JE and JEn.

As a result, JEls'''n detects defects with extreme characteristics of picture defects, and JE2 to JE, , detect defects with intermediate characteristics.

These determination elements JE□ to JE1. Nou or any one
When an output indicating that the paper is wasted is generated at any time, it is output =)OR
A paper waste signal is output from

FIG. 6 shows the internal configuration of determination element JE in the circuit of FIG. 5. In this circuit, sample data S and sample data T are applied to the absolute difference circuit 22, and l5-Tl is taken out and applied to the B input of each comparator. On the other hand, the sample data S is in the A input of the con A lake.
Based on this, the tolerance value generation circuit 21 gives the tolerance value E.

There are various ways to give this allowable value E. For example, a different tolerance value may be fixedly given to each pixel. Here, a value obtained by multiplying the gradation of a sample pixel by a fixed ratio (0 to 1) is set as an allowable value to be given to the sample pixel corresponding to that sample pixel. As a result, the allowable value generation circuit 11 receives sample data S that is input sequentially.
is multiplied by a fixed ratio (0 to 1) to generate a gradation difference tolerance E.

The controller determines whether the absolute value of the difference +19-TI is greater than the gradation difference tolerance E (Is-Tl>E), and when it is greater, gives a sinking defect number to the counter.

The counter counts the defective signals, and this count represents the number of defective pixels. Is this count value Con)I? The number of defective pixels is compared with the allowable number of defects from the latch addition by the controller 5, and it is determined whether the number of defective pixels exceeds the allowable number of defects, and when the number of defective pixels exceeds the allowable number of defects, a paper waste signal J is output.

Figure 7 shows the gradation difference tolerance generation circuit 1 in the circuit of Figure 6.
1 shows the internal configuration of the circuit 1. This circuit is composed of the same number of buffers B as the number of bits of the input signal. In this case, since the sample data S has 8 pits, there are 8 buffers, 2 of which take the start as input and output as the MSB, and the next 6 pits store the upper 6 bits of the sample data S including the MSB. Assume that the data is taken out via buffer B.

The LSB 2t of the sample data S is not connected.

As a result, the 8-pit sample data S is bit-shifted in the LSB direction, and a gradation difference tolerance E of 12.5% of the sample data S is obtained. By changing the number of bits shifted in an appositional manner, the gloss%, 25%, 6.25%, 3.
A value such as 125% is obtained. To obtain other values, T
A multiplier such as TL may be used.

FIG. 8 shows the internal configuration of the absolute difference circuit 22 in the circuit of FIG. Exclusive off circuit 32. The main components are an adder 33 and an inverter 34. Since this lIJ circuit is well known, a detailed explanation will be omitted, but it obtains sample data S and sample data 〒 and outputs the absolute value l5-Tl of the difference between them.

As described above, the present invention sets a plurality of combinations of the gradation difference tolerance value between the sample pixel and the sample pixel and the defect n+J+prime number tolerance value exceeding this tolerance value, and detects defects by any of these combinations. Since it is determined that there is a pattern defect when a defect occurs, a wide variety of defects can be reliably detected, unlike conventional methods in which the nature of defects that can be detected is fixed.

As a result, inspection accuracy can be greatly improved.

Moreover, the device configuration is simple.

[Brief explanation of the drawing]

Figure 1 is a diagram showing the IF/7 configuration of the image information detection section of the pattern inspection device that is the object of the present invention, and Figure 2 is a schematic explanatory diagram of sample data and sample data arrangement method for pattern inspection. , FIG. 3 is a characteristic diagram showing the relationship between the allowable judgment level for defect detection and the number of 8′1 defects, and FIG. 4 is a block diagram showing the configuration of the pattern inspection device Todoroki according to the present invention. FIG. 5 is a circuit diagram showing the internal configuration of the determination circuit in the circuit of FIG. 4;
6 is a circuit diagram showing the internal configuration of the determination element in the circuit of FIG. 5, and FIG. Fig. 8 is a circuit diagram showing the internal configuration of the absolute value circuit of the difference in the 11!l path of Fig. 6. ■...Printed "Proboscis, 2...Camera, 3...Cylinder. 4...・Rotary encoder, 5.6...memory. JE...judgment), OR...or gate. B...sutsufu completion, S...sample data, T...sample data. Applicant Agent Kiyoshi Inomata 3rd cause

Claims (1)

[Scope of Claims] 1. In a method for detecting missing levels in a pattern by decomposing a pattern of a sample print into a pixel matrix and sequentially comparing density gradations with pixels in the pattern of the sample print corresponding to each pixel, Multiple combinations of a tolerance value for the gradation difference between a pixel and a sample pixel and a tolerance value for the number of defective pixels exceeding this tolerance value are set, and there is a defect that corresponds to any of these combinations. A pattern inspection method for printed matter characterized in that it is determined that there is a pattern defect based on 5. 2. A device for forming a synchronization signal according to the conveyance operation of the printed matter, and a device for scanning the pattern of the printed matter based on the synchronization signal. A camera for extracting image information from sample prints, a memory into which image information extracted from sample prints by this camera is written, a tolerance value for the gradation difference between sample pixels, and a number of defective pixels exceeding this tolerance value. a determination circuit having a plurality of determination elements each having a plurality of combinations with tolerance values set, and outputting a defect signal when any of the determination elements determines a defect based on image information of a sample print from the camera; A pattern inspection method for printed matter.