JPH0418768B2 - - Google Patents

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention provides an inspection method that images a printed pattern, processes the image, and inspects mainly local defects such as cuts, chips, or blurs in the printed pattern. Regarding.

[Conventional technology]

Conventionally, quality inspection of printed patterns using image processing technology has been carried out exclusively by determining the area value of the entire printed pattern and determining whether or not this area value is within a predetermined tolerance range.

[Problem that the invention seeks to solve]

However, although such a method can roughly inspect the quality of a printed pattern, it is difficult to inspect for defects due to partial concave or convex portions of the pattern or to inspect for differences in fine patterns such as printed characters.
This is because in patterns such as printed characters, the area value of the characters varies greatly depending on the degree of ink adhesion, so it is not possible to properly determine criteria for distinguishing between non-defective products and defective products.

Therefore, it is an object of the present invention to enable accurate inspection of the quality of fine patterns such as printed characters, even if there are variations in print thickness.

[Means for solving problems]

Window setting means for setting a group of predetermined shaped windows (chain windows) that are adjacent to each other along the printed pattern to be inspected, and area data extraction means for extracting area value data occupied by the printed pattern portion for each set window. and calculation means for performing various calculations including comparison with set values based on the area value data.

[Effect]

After capturing an image of the print pattern with an imaging device such as a television camera and converting the captured image signal into a binary signal according to the density level, a window of a predetermined shape covering at least the width of the pattern is formed along the shape of the pattern. The pattern area value is determined for each window by setting several adjacent windows, and depending on whether or not this area value is within a predetermined tolerance range, mainly local defects such as print chips, cuts, blurs, and protrusions can be detected. To enable accurate detection. Note that the judgment content can be adjusted by appropriately combining judgments based on differences in pattern area values between adjacent windows, judgments based on the number of windows whose pattern area values are within a predetermined standard, judgments based on envelope windows, etc. and improve accuracy.

〔Example〕

FIG. 1 is a reference diagram for explaining an embodiment of the present invention, FIG. 2 is a block diagram showing the configuration of an image processing apparatus in which this invention is implemented, and FIG. 3 is a reference diagram for explaining a specific example of defect inspection. FIG.

First, FIG. 2 will be explained. In addition, in the same figure, 1 is a printed pattern to be inspected, and 11 is a printed pattern to be inspected.
12 is an analog/digital (A/D) converter, 13 is a window generator, 14 is an image memory, 15 is a feature data extraction unit, 16 is a processing device such as a microprocessor, 17 1 is an input/output (I/O) interface section, and 18 is an operation display section.

The television camera 11 images a pattern 1 such as printed characters and converts it into an electrical signal (image signal). This image signal is applied to the A/D converter 12, where it is converted into a binary digital signal according to its gray level and stored in the image memory 14. The feature extraction unit 15 extracts various feature data including area data of the print pattern 1 from the image memory 14, and the processing device 16 performs various calculation processes including comparison based on this feature data. Window generation part 1
3 performs window settings based on instructions from the processing device 16, and selects feature data to be read from the image memory 14. This window specifies the area to be observed or inspected on the imaging screen, and the position and shape to be generated can be stored in advance in a predetermined memory, or can be displayed using the I/O interface using the operation display unit 18. Settings can be made by providing window information to the processing device 16 via the face unit 17. This window information is appropriately processed in the processing device 16 and then provided to the window generation section 13.
Incidentally, such a method of generating a window is already known, and is disclosed in, for example, Japanese Patent Laid-Open No. 189780/1983.

FIG. 1 shows the relationship between the window and print pattern set in this way.
is a print pattern, and 2 ₁ , 2 ₂ . . . 2n is a window. In the figure, 3 is an envelope window, 4 is an area outside the window, that is, the background, and 5 is dirt (noise).

That is, Fig. 1 shows the printing pattern (here,
This is an example of setting n circular windows 2 ₁ , 2 ₂ . . . 2n adjacent to each other along the shape of the number "2")1. It can be set by providing position information of the window, diameter information representing the diameter of the window, etc. Then, by setting such a series of windows (chain window), pattern area data for each window can be obtained from the feature data extraction unit 15, so that the processing device 16 converts each area data into a predetermined value. By comparing with the upper and lower limit set values,
Defects can be identified.

For example, if the printed pattern is chipped, cut, or faded, the area value will be less than a predetermined value, and
Conversely, protrusions and the like can be detected because their area values are greater than or equal to a predetermined value. Figure 3 (b) is an example where cuts 6 ₁ and 6 ₂ occur in the printed pattern 1 ₂ .
Figure C shows an example in which chipping or fading 6 ₃ and protrusions 6 ₄ occur. In addition, character pattern 1 in A of the same figure
In ₁ , the character width is narrower than in B, but this is an example of a normal case; by selecting the upper and lower limit settings appropriately, pass/fail inspection is possible regardless of the character width. This shows that. In addition, partial defects such as chips, cuts, scratches, or protrusions as mentioned above can be detected not only by the area occupied by one window, but also by determining the difference between adjacent windows and comparing this with another set value. By using these methods in combination, inspection accuracy can be improved.
In other words, this method utilizes the fact that when the difference in area values between adjacent windows is calculated, the difference is approximately zero in a normal case, but becomes a significant value in the case of a defect. Furthermore, the processing device 16 calculates the number of windows whose area values are within a predetermined tolerance range, and compares this number with another set value to determine whether the print pattern of interest is of a different type. It is possible to determine whether On the other hand, it goes without saying that the determination can also be made from the number of windows whose area values do not satisfy a predetermined condition, and this is similar to using a background value instead of the area value of each window.

Also, in Fig. 1, envelope window 3 is generated, but this is generated by chain window 2.
It is automatically generated from each position data of ₁ to 2n, and is provided to separate the print pattern 1 from the background 4. In other words, this envelope window 3
By providing , patterns outside this envelope window can be regarded as different types of patterns, and patterns with this different type can be treated as if pattern 1 is a different pattern or as having dirt 5. . Note that the width of the envelope window 3 is set to be slightly larger than the size of the individual windows 2 ₁ , 2 ₂ . . . 2n.

The above explanation deals with the case where there is only one pattern to be inspected, but if there are multiple printed patterns such as numbers or character strings, the chain window as described above can be set up separately for each pattern. It is done. Further, although a circular window is set in the above example, it goes without saying that the shape is not limited to a circle.

〔Effect of the invention〕

According to this invention, a plurality of window groups are generated and quality judgment is made for each individual window, so that partial defects such as cuts, chips, scratches, or protrusions in the pattern can be detected based on the thickness of the pattern. As a result, the test accuracy and reliability can be significantly improved. In addition, inspection content can be improved by not only making judgments for each individual window, but also making judgments between windows, such as determining the difference in pattern area values between adjacent windows and comparing this with a set value. It is possible to further improve accuracy. Furthermore, by determining the number of windows that satisfy the set criteria and by setting an envelope window that includes the chain window, there is an advantage that noise components such as print pattern differences and dirt can be accurately inspected.

[Brief explanation of drawings]

FIG. 1 is a reference diagram for explaining an embodiment of the present invention, FIG. 2 is a block diagram showing an image processing apparatus in which this invention is implemented, and FIG. 3 is a reference diagram for explaining a specific example of defect inspection. It is a diagram. Code explanation, 1, _{1 1} , 1 ₂ ...Print pattern, 2
₁ ~ 2n...window, 3...envelope window,
4... Area outside the window (background), 5... Dirt,
6 ₁ to 6 ₄ ...Minute defects, 11...TV camera (imaging device), 12...Analog/digital (A/
D conversion section, 13... Window generation section, 14...
Image memory, 15... Feature extraction section, 16... Processing device (microprocessor), 17... Input/output (I/O) interface section, 18... Operation display section.

Claims (1)

[Scope of Claims] 1. A method for inspecting a printed pattern, which images a printed pattern and performs image processing including at least binarization for inspection, the method comprising: imaging a reference printed pattern in advance and binarizing it; A predetermined number of adjacent print pattern inspection windows of a predetermined shape are successively set along the print pattern area of the image obtained by using a means for inputting information regarding the position and area of the window. At the same time, the area value occupied by the printed pattern portion is determined for each window, and a predetermined setting value for comparison is set based on this area value. The setting value data is stored in a storage means for storing, and then the print pattern inspection is performed on the print pattern to be inspected obtained by imaging and binarizing the print pattern to be inspected. After generating a window for each window and determining the area value occupied by the print pattern portion to be inspected for each window, the area value and the setting value corresponding to each window position read from the setting value data storage means are calculated. 1. A method for inspecting a printed pattern, characterized in that it enables mainly partial inspection of a printed pattern by performing predetermined calculations including comparison.