JPH028257B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a surface inspection device for inspecting defects on the surface of a member to be inspected, such as a sheet material, and particularly relates to a signal processing method for ranking the weight and weight of defects closer to visual inspection. be.

BACKGROUND ART Mechanical inspection techniques using light are in practical use as inspection techniques for defects occurring on the surface of sheet materials such as paper, cloth, and metal. However, defects recognized by such mechanical defect inspection techniques and defects recognized by visual inspection often do not match. In other words, in mechanical inspection, if a defect is accompanied by discoloration or large irregularities, even a very small defect will generate a large signal, whereas in visual inspection, if the defect is not larger than a certain area, it is difficult to see how large discoloration or irregularities occur. Even if it is, it cannot be recognized as a defect. On the other hand, even a very mild discoloration can be easily recognized by visual inspection if it has a large area, whereas a mechanical inspection machine can only obtain a minute signal corresponding to a slight discoloration. Figure 1 is a conceptual diagram showing how signals are used in conventional mechanical inspection technology, where 1 indicates a defect in the sheet material 2, W indicates the defect width, and m ₁ to _{m 5} each indicate a scanning line spanning the defect. , m ₁ to _{m 5} The peak value of the defect signal obtained for each scanning line is V ₁ to _{V 5} (not shown)
shall be. m ₁ for defects such as those shown in Figure 1.
The information read by the scanning line of ~ _m5 is the defect width W,
These are the defect length as the number of scanning lines where the defect occurred, and the signal peak values from V ₁ to V ₅ . However, the peak value of the defect signal is an analog signal that changes moment by moment over the entire length of the defect, and it is very difficult to process it, so the defect is often represented by its maximum value. Therefore, conventional mechanical defect inspection machines only measure the presence or absence of defects, defect width, defect length, and maximum value of defect signals. However, in visual inspection, subtle changes in the reflectance of defective areas are an important parameter that determines the weight and weight of defects, so in reality, defect inspection of sheet materials, where a wide variety of defects occur, is performed under conditions close to visual inspection. It is difficult to carry out this process, and it has been a problem to apply mechanical inspection devices to the line as a representative of visual inspection.

The present invention was made in response to the current situation, and
The wave height value of the defect signal is roughly divided into multiple ranks, and the presence or absence of the defect signal in each category is weighted and aggregated for each scanning line, and the aggregated result is divided by the number of scanning lines in which defects have occurred. This allows a mechanical defect inspection machine to perform statistical evaluation of defect symptoms, which is similar to the macroscopic evaluation of defects visually observed.

An embodiment of the present invention will be described below with reference to the drawings. For convenience of explanation, the symptom classification of defects will be roughly divided into severe, medium, and light defects. Second
The figure shows an embodiment of a circuit for carrying out statistical signal processing according to the present invention. In the figure, 9 is a defect signal, and 10, 11, and 12 are different reference voltages.
Waveform shaper with v ₁ , v ₂ , v ₃ , 13, 14, 1
5 is a circuit for correcting the output of each pulse counter, weighting each pulse counter, and calculating the sum; 19 is the number of defective scanning lines; 1;
7 receives the circuit output of 16 and sends the data to 19
18 is a circuit that receives the output of the division circuit 17 and determines the defect symptoms; 2
0, 21, and 22 are respectively heavy, medium, and light defect symptom outputs, v ₄ and v ₅ are reference inputs for determining the defect symptoms, and N ₁ , N ₂ , and N ₃ are weight evaluation values. In addition, for the sake of explanation when explaining the operation of this circuit, the defects are m ₁
Assume that it occurs for 5 scanning lines of ~m ₅ ,
The peak value of the signal generated for each scanning line is V ₁ ~
Let's say V ₅ . A defect signal 9 generated by the inspection machine is input to a waveform shaper. 10 is a waveform shaper for detecting major defects, ₁₁ is a medium defect, and ₁₂ is _a waveform shaper for detecting light defects. A pulse signal is generated at the output of the device, and the number of pulses is counted by counters 13, 14, and 15, respectively. That is, depending on the peak value of each defect signal from _V1 to _V5 , the number of heavy, medium, and light defects is counted by 13 to 15 counters for each scanning line. By the way, when 1 count of pulses is counted by 13 counters, 1 count of pulses is counted by the same signal.
Counters 4 and 15 also count one count. This is obvious from the relationship between signal magnitudes and the properties of the waveform shaper. Therefore, the accurate number of heavy, medium, and light defects is calculated by subtracting the counter count value of 13 from the count value of 14. number of defects,
Similarly, the number of minor defects is obtained by subtracting the counter count value of 14 from the counter count value of 15.
The circuit No. 16 performs this calculation in advance and also calculates (number of heavy defects x weight N ₁ ) + (number of medium defects x weight N ₂ ) + (number of light defects x weight N ₃ ). The calculation output from the 16 circuits is divided by the 17 circuit, which is the input number of defective scanning lines, 19. The circuit number 18 receives the result calculated by the circuit number 17, and its value is preset. If it is v4 _or more, it is considered a major defect and outputs a signal of 20, _v4 to _v5
If so, a signal output of 21 is generated as a medium defect, and a signal output of 22 is generated as a light defect if it is less than _v5 . Thus the second
In the signal processing circuit shown in the figure, the defect signal for each scanning line is first classified into severe, medium, and light symptoms, and then the number of defects is counted for each symptom, weighted, and averaged by the number of scanning lines. However, when considering human visual inspection, if a defect with a large change in reflectance (major defect) exists in a continuous defect, the length of the part and the occurrence rate in the continuous defect are determined to be defects. This is an important factor in determining the symptoms of a defect, and even if there is a change in reflectance equivalent to a major defect, if the major defect exists only in a minute part of a continuous defect, it is rather an average defect symptom. It goes without saying that the signal processing method of the present invention allows for evaluation of defect symptoms closer to visual observation, since the corresponding continuous defect is evaluated based on the average reflectance of the defect, defect length, and defect width. Nor.

For convenience of explanation, the above explanation describes cases in which defect symptoms are broadly classified into three categories: severe, medium, and light; however, defect symptom categories are not limited to these three types and can be freely selected. Needless to say, it is possible.

As described above, according to the present invention, the signal peak value of one entire defect is ranked for each scanning line, added up while adding weight, and divided by the defect length to statistically evaluate the symptoms of the defect. It is expected to have practical benefits, such as processing and being able to perform evaluations similar to visual inspection.

[Brief explanation of drawings]

FIG. 1 is a conceptual diagram showing defect information obtained by a mechanical inspection machine, and FIG. 2 is a block diagram showing signal processing of the apparatus according to the present invention. In the figure, 1 is a sheet material, 2 is a defect, 9 is a defect signal,
10, 11, 12 are waveform shapers, 13, 14, 1
5 is a pulse counter, 16 is a correction calculation circuit, 1
7 is a divider, 18 is a defect ranking circuit, 19
is the number of scanning lines where defects occur, 20, 21, and 22 are ranked defect signals, m ₁ to _{m 5} are scanning lines, V ₁ to V ₅ are defect signal peak values, v ₁ to _{v 5} are reference voltages, N ₁ to _N3 is the weighted evaluation value, and W is the defect width. In the drawings, the same reference numerals indicate the same or corresponding parts.

Claims (1)

[Claims] 1. A counting means for ranking the defect signals obtained by scanning the surface of the member to be inspected for each predetermined peak value, and counting the number of defect signals for each rank, and assigning a predetermined weight to the counted value by this counting means for each rank. comprising a totaling means for totalizing the total number of defects, a divider for dividing the total result value by the totaling means by the number of scans in which a defect has occurred, and a rank determining circuit for determining the rank of all defects from the output of the divider, A surface inspection device characterized in that a signal from a defect is statistically evaluated over the entire defect.