JPS61107143A - optical surface inspection equipment - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to an optical surface inspection device that detects pinholes on the surface of a pipe, for example, and particularly relates to an optical surface inspection device that detects defects from input signals with shading. This invention relates to improvements to surface inspection equipment.

[Conventional technology]

Figure 4(,) shows, for example, Automation, Volume 2a, No. 11.
10 diagrams of conventional optical surface inspection equipment shown in the issue,
Figure 4 (6) is the main timing waveform.

In the figure, (1) is the material to be inspected, (2) is a defect such as a pinhole, (3) is a -dimensional image sensor, (4) is the field of view of the sensor, and (5) is the threshold for setting the threshold. The shoulder setting device (6) is the image sensor (3
) A comparator to binarize the analog signal from.

(7) is a shift register, and (8) is a defect signal corresponding to defect (2).

A conventional optical surface inspection device is configured as described above, and allows a person to visually inspect defects (2) such as pinholes and stains on a flat test material (1) such as a tape-shaped metal foil or paper or cloth. Defects (2) are automatically detected optically instead of inspection.

The test material (1) moves in the direction of the arrow in the figure, and the field of view (4) of the image sensor (3) is set perpendicular to the moving direction of the test material +11.

When the defect (11) moves and enters the field of view (4), the image sensor (3) detects the defect and a video signal as shown in waveform a in Fig. 4 is obtained.At this time, the defect signal (8) corresponds to defect (2).

The comparator (6) binarizes the video signal from the image sensor (3) and supplies it to the driver circuit (7).

Here, the control device 1 creates timing for driving external devices such as a display and an alarm, and also supplies power to the outside.

The threshold (9) is the threshold setter (5
), and the comparator (6) compares the two inputs to obtain a binarized output as shown in the waveform of FIG.

[Problem that the invention seeks to solve]

In conventional optical surface inspection equipment as mentioned above.

The shape of the material to be inspected (1) is flat and numerous, the amount of light reflected from the part where the defect (2) does not exist is constant, and the part other than the defect signal (8) is flat as shown in waveform a in Figure 4. If a negative video signal is obtained, it is converted and binarized using threshold (9), and only the signal corresponding to defect (2) can be obtained as shown in the waveform of FIG. However, if the shape of the material +11 to be inspected is, for example, a pipe, the amount of reflected light is small in the periphery, and a background area with a low level of defect signal (8) appears. ), it becomes impossible to extract only the defects. In addition, when defect (2) is a pinhole or the like that occurs in a metal weld, many minute signals similar to defect (2) are generated from the weld surface other than the pinhole, and the appearance of the similar defect is There are various problems depending on the welding method, the material of the material to be tested (1), etc., and conventional methods cannot distinguish between them.

This invention was made to solve this problem, and detects defects mixed with minute noise similar to defects and materials to be inspected in which only video signals with shading are obtained that do not have a flat background level. The purpose is to

[Means for solving problems]

The optical surface inspection device according to the present invention extracts only defect signals from a shaded background.
We decided to have a means for generating gate metal to effectively process only the areas where defects may occur within the field of view of the image sensor. The position and size of this gate can be set using a digital switch according to the type of material to be inspected.

In addition, in order to eliminate similar defects such as minute reflections from welding surfaces other than defects, the minimum size to be determined as a defect can be set in two dimensions in the X and Y directions using a digital switch. It is something.

[Effect]

In this invention, in order to remove the background with shading, such as when detecting a pinhole in a pipe weld, the position and size of the gate are optimally set, thereby eliminating the influence of shading. Defects can be detected, and by setting the defect size judgment value optimally using a digital switch, it is possible to remove defects mixed with similar minute defects from the welding surface, etc., and remove similar minute defects. Only the defects you want to detect can be detected.

〔Example〕

FIG. 1 is a block diagram showing an embodiment of the present invention.

FIG. 2 shows the main waveforms of each part, and (1) to (9) are exactly the same as the conventional device described above.雛 is the gate generation circuit, αυ is the digital switch, az is the AND gate, a
3 is a filter circuit for removing similar minute defects, (I
4 is a timing generation circuit for supplying timing to each part, αS is a video signal with shading, (1
e is a defect signal after binarization corresponding to defect signal (8), and fin is an unnecessary signal due to shading.

In the optical surface inspection device configured as described above, the comparator (6) compares the video signal from the image sensor (31) with the threshold (9) and converts the binarized signal as in the conventional device. AND gate (supplied to a. Digital switch (11a) K Yo') Data and digital switch (1
1b) After the data for setting the size of the gate is input to the gate generation circuit a, a gate is created and supplied to the AND GO (13).

In the AND gate α2, only the binary video signal in the gate generated by the gate generation circuit (I[l) is considered valid and supplied to the filter circuit (13a) in the X direction, and The filter circuit (13b) in the y direction passes only defects larger than the detection size in the direction.
).

Similarly to the X direction, the filter circuit (15b) in the , direction also passes only defects that exceed the detection level set by the digital switch (11d) and supplies them to the driver circuit (7). The timing generation circuit α supplies clocks corresponding to each element of the image sensor to the gate generation circuit (1G) and the X-direction filter circuit (13a), and also supplies a clock corresponding to the scanning period in the X-direction to the ky-direction filter circuit (1sb). supply to

Next, the waveforms of the main signals in each part will be explained with reference to FIG.

Waveform a is an analog video signal from the image sensor (3), and the background level other than the defect signal (8) is not flat but has shading.
8) Since it is very low, the threshold (9)
When the output from the comparator (6) is binarized, unnecessary signals (17a) and (17b) appear on both sides in addition to the defective signal ae after binarization, as shown in the waveform shown in FIG.

Therefore, a gate like waveform C is generated in the gate generating circuit al, and the times of T1 and T2 are set by digital switches (11a) and (11b).

The input waveform of AND gate q3 is waveform C),
Its output is waveform d. Therefore, as the output of the AND gate (L), the video signal α9 with shading is
Only the defect signal can be extracted from the

Next, although various algorithms and circuits can be considered for the filter circuit 0, a specific example will be explained with reference to the drawings.

Figure 3 (,) is an example of a specific circuit, Figure 3 (b) is a cross section of the defect before it passes through the filter, and Figure 3 (C) is
This is a diagram showing a cross section of a defect after passing through a directional filter, or a shift register, which is a read-only memory.

The X-direction filter circuit (13a) and the Y-direction filter circuit (13b) are similar in design, and are shown in the block diagram of FIG. 3a. A shift register (18 converts the binarized video signal into parallel data and supplies it to memory 0.Memory AL receives and receives the video signal converted into parallel and data from the digital switch. The contents of memory 0 are written so that a signal is output only when the video signal is larger than a set size.

Figure 3(b) is a diagram showing the cross section of the defect before passing through the filter, and the solid line indicates that the beam scanned above the defect in the x direction, which is represented by six scanning lines. has been done. This defect can be fixed using a digital switch (11c).
When the number of filter stages in the X direction is set to 2, only the solid line portion of 2 pixels or more in the X direction is passed, so the cross section of the defect passing through the filter circuit (13a) in the X direction is the third
The four scanning lines shown as solid lines in the diagram (C) pass through.

Hypothetically, if the number of filter stages in the y direction is set to 4 or less, the output of the filter circuit (13b) in the y direction appears and it is determined that a defect exists, but if the number of filter stages is set to 5 or more, is determined to be free of defects.

By the way, in the above description, the position and size of the gate and the number of stages of the filter are set by digital switches, but the setting means is not limited to this, and various setting methods such as a keyboard or an external control device can be considered.

Furthermore, although the threshold for binarization is explained as being set by the volume, this is only for convenience of explanation.

It is also possible to adaptively vary the threshold using the average level within the gate.

〔Effect of the invention〕

The present invention has been described above by using a gate whose position and size can be varied and a filter whose defect detection size can be set two-dimensionally.

This has the effect of making it possible to detect only defects mixed with similar minute defects in a shaded background.

Therefore, it has the effect of making it possible to detect defects that are difficult to detect with conventional equipment, such as bottle holes that occur in pipe welds.

[Brief explanation of the drawing]

FIG. 1 is a block diagram showing one embodiment of the present invention. Figure 2 is a diagram for explaining the main waveforms of each part in Figure 1.
FIG. 3 is a diagram illustrating an embodiment of the filter circuit of the present invention, and FIG. 4 is a diagram illustrating a conventional surface inspection apparatus. In the figure, (1) is the material to be inspected, (2) is the defect, and (3)
is an image sensor, (4) is a field of view, (5) is a threshold setter, +61 is a comparator, and (7) is a driver circuit. (8) is the defect signal, (9) is the threshold, (I
l is the gate generation circuit, αυ is the digital switch, aa
(13 is a filter circuit, (L4 is a timing generation circuit, video signal with as+h shading. ae is a defective signal after binarization, αn is an unnecessary signal, αυ is a shift register, (II is a memory It is.

Claims (1)

[Claims] In an optical surface inspection system that detects defects in a material to be inspected using a reflection method using a one-dimensional image sensor installed so that the direction of movement of the material to be inspected is perpendicular to the field of view of the sensor, the gate from the starting point of the sensor scan is used. a first means for generating a gate whose position and size can be varied; and a minimum value that is considered to be a defect among the defect signals in the gate generated by the first means can be two-dimensionally set. An optical surface inspection device comprising: a second means.