JPH045941B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a defect inspection device that automatically and accurately inspects flaws on the surface of a sheet-like object.

2. Description of the Related Art Conventionally, an apparatus has been proposed that irradiates light onto a sheet-like object, which is an object to be inspected, and causes the reflected light to enter a sensor to inspect flaws on the surface of the sheet-like object.
However, conventional inspection devices have the disadvantage that it is difficult to detect smoothly changing flaws, small flaws that are continuous in the feeding direction of the sheet-like object, and the like.

This invention has been made in view of the above points. The present invention will be explained below with reference to the drawings.

FIG. 1 is a schematic diagram of the overall configuration showing one embodiment of the present invention. In this figure, 1 is a low-pressure sodium lamp, 2 is a CCD camera, 3 is a sheet-like object to be inspected, and 4 is a roll. The reflected light is imaged by a CCD camera 2. 1
0 is a processing circuit.

The low-pressure sodium lamp 1 and the CCD camera 2 are fixedly provided in a housing 5 as shown in FIG. 2 so that the relationship between them is constant. 6 is a cylindrical lens, and θ is set at 60°.

FIG. 3 is a block diagram showing the internal configuration of the processing circuit 10, in which 11 is a + direction large defect detection section, 12 is a one direction large defect detection section, 13 is a small defect collection defect detection section, and 14 is a gradual defect detection section. 15 is an accumulator having at least 2048 cells of memory; 16 is a linear minute defect detector; 17 is a suppression circuit;
The operation of the accumulator 15 is stopped when an output is output from any one of the sections 14. 18 is an exclusive logic block.

Next, the operation of each part will be sequentially explained.

Only noise is extracted from the output of the CCD camera 2 (FIG. 1), its level is calculated, the noise level is determined, and the threshold level is determined by multiplying that value by a required coefficient. A signal above this threshold level becomes a signal representing the state of scratches on the surface of the sheet-like material 3.

As shown in FIG. 4, the + direction large defect detection unit 11 outputs an output signal S ₁₁ when the + direction amplitude D of the output signal S of the CCD camera 2 is greater than or equal to a predetermined value D _A. This signal is also applied to the suppression circuit 17 to stop the operation of the accumulator 15.

As shown in FIG. 5, the one-way large defect detection unit 12 detects when the amplitude D in one direction of the output signal S of the CCD camera 2 is greater than or equal to a predetermined value D _B.
Gives an output signal S ₁₂ .

The small defect collective defect detection section 13 outputs an output when the number of defects (scratches) is large, although each defect (scratch) is small. In other words, as shown in Figure 6 a and b, when there are a predetermined number of amplitudes N C or more in the positive direction or one direction that are larger than the predetermined value D _CP during a certain period of time (for example, 200 _msec ). , gives an output signal S ₁₃ .

The gradual defect detection section 14 detects defects that change smoothly. That is, FIG. 7a shows the data accumulated in the accumulator 15,
FIG. 7b shows the output signal for one scan obtained in the current scan. What is shown by the dotted line in FIG. 7b is the accumulated data of FIG. 7a, and the gradual defect detection section 14 integrates the difference. That is,
Integration is performed by calculating the difference between the cumulative value in each cell of the CCD camera 2 and the value in the current scan corresponding to each cell. In this case, the fine irregularities on the left and right sides of Fig. 7b are due to noise, and therefore, when integrated, they are canceled by + and -, so the integral value D _I obtained in this way is the same as when there is no slow defect. is approximately 0, but if there is a gradual defect as shown in FIG. 7b, the area of the shaded area is detected and becomes a large value. When the integral value D _I becomes larger than a predetermined value D _D , an output signal S ₁₄ is output. This makes it possible to detect defects that change smoothly.

The linear minute defect detector 16 is intended to detect defects that are continuous in the feeding direction of the sheet-like material 3.

That is, the current value accumulated in the accumulator 15
Add the following operation to Y _OLDi to create a new Y _NEWi .

Y _NEWi ←Y _OLDi +S _i C _E /1+C _EHere , i=1, ..., 2048 S _i is the current signal value C _E is the cumulative weight (for example, 0.1) and the predetermined value determined by Y _NEWi Outputs output signal _S16 when D is greater than or equal to _E.

First of all, the cumulative value Y used here is not a value obtained by simply adding, but is obtained by multiplying the weighted average value Y _OLDi up to that point and the newly obtained output signal value Si by weighting C _E. , is divided by (1+C _E ) to obtain a weighted average value, and this is called the cumulative value Y, which is set as Y _NEWi =Y _OLDi+1 .

Such a value is usually expressed as Y _NEWi = Y _OLDi・t+Si(1-t) (0≦t≦1), but in actual digital circuits, the number to be divided (1+C _E ) is By making it a power of 2 (for example, C _E = 1, 3,
7, etc.), which allows division to be processed at high speed. In other words, the equation for Y _NEWi above is a written arithmetic equation performed in an actual circuit, and is 1/
If (1+C _E )=t, then it becomes a commonly used weighted average formula.

The above cumulative weight C _E was set to 0.1 as an example, but
This can be determined appropriately; if you want to avoid detecting small scratches, you can set it to a small value, and if you want to detect it strictly, you can set it to a large value. Y _NEWi is accumulated for each cell, and this value does not immediately indicate a linear minute defect, but only when this value is equal to or greater than a predetermined value D _E is determined to be a linear minute defect.

Note that, as a self-diagnosis function, diagnosis is performed based on the number of defect detection signals per unit time. For example, 1
If the number of detected defects is 0 at a given time, an alarm is lit. In addition, when the number of detected defects exceeds a predetermined number within 10 seconds, an alarm is lit, and when this condition continues for 30 seconds, in addition to the alarm, a buzzer sounds and the output of the output signal is prohibited. In this case, the reliability of the test can be further increased.

In addition, although the surface of the sheet-like object 3 was scanned by the CCD camera 2 in the above, a solid-state image sensor can generally be used for this purpose. Further, when the width of the sheet-like object 3 is wide, a plurality of CCD cameras 2 are arranged side by side, and a processing circuit 10 is provided accordingly.

As explained in detail above, the present invention digitally accumulates output signals for one scan in an accumulator, and uses a linear minute defect detector to multiply this accumulated value by a predetermined weight and calculate the corresponding output signal. Accumulate sequentially,
Since linear minute defects are detected from this value, even shallow scratches on the surface of the sheet-like object can be reliably detected as long as they are continuous.

Furthermore, in this invention, a slow defect detection section is provided,
The difference between the output signal indicating the accumulated value up to the previous time stored in the accumulator and the output signal for the current one scan is calculated and integrated for each corresponding output signal, and slow defects are detected using this integrated value. Therefore, it has the advantage of being able to detect even smoothly changing scratches.

[Brief explanation of drawings]

FIG. 1 is a schematic diagram of the overall configuration showing an embodiment of the present invention, FIG. 2 is a diagram showing the relationship between a low-pressure sodium lamp and a CCD camera, and FIG. 3 is a diagram showing the internal configuration of a processing circuit of the present invention. 4, FIG. 5, FIGS. 6a and 6b, and FIGS. 7a and 7b are waveform diagrams for explaining the operation. In the figure, 1 is a low-pressure sodium lamp, 2 is a CCD
A camera, 3 a sheet-like object, 4 a roll, 10 a processing circuit, 11 a + direction large defect detection section, 12 a unidirectional large defect detection section, 13 a collection of small defects detection section, and 14 a gradual defect detection section. part, 15 is an accumulator, 16
1 is a linear minute defect detector, 17 is a suppression circuit, and 18 is an exclusive logic block.

Claims (1)

[Scope of Claims] 1. An apparatus for illuminating a sheet-like object to be inspected, receiving the reflected light with a CCD camera, and detecting flaws on the surface of the sheet-like object from the output signal of the CCD camera, comprising: an accumulator that digitally accumulates and stores output signals for one scan of the sheet-like object by the CCD camera; and an accumulator that multiplies each of the output signals stored in this accumulator by a predetermined weight and sequentially outputs the corresponding output signals. 1. A defect inspection device for a sheet-like object, comprising: a linear minute defect detector that outputs a linear minute defect signal when the accumulated value reaches a predetermined value. 2. In an apparatus for illuminating a sheet-like object as an object to be inspected, receiving the reflected light with a CCD camera, and detecting flaws on the surface of the sheet-like object from an output signal of the CCD camera, the sheet-like object is detected by the CCD camera. an accumulator that digitally accumulates and stores output signals for one scan of a shaped object; each of the output signals stored in this accumulator is multiplied by a predetermined weight; the corresponding output signals are sequentially accumulated; a linear minute defect detector that outputs a signal of a linear minute defect when reaches a predetermined value, an output signal indicating the accumulated value up to the previous time stored in the accumulator, and an output signal for one scan of the current time. and a gradual defect detection section that takes and integrates the difference for each corresponding output signal and outputs a signal of a gradual defect when the integrated value reaches a certain value. Inspection equipment.