JPH0528780B2 - - Google Patents

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to metal strips, etc. in the manufacturing process.
The present invention relates to a method of optically inspecting the surface of a moving object for defects.

[Prior art and problems to be solved by the invention]

A device that optically inspects surface defects on metal strips uses a two-dimensional imaging device such as a television camera to capture a still image of the strip, and uses image processing technology to inspect the presence or absence of defects. In some cases, they are classified according to their importance, etc. However, such a device processes a huge amount of data, making the device extremely large and expensive.

Therefore, we record still images on magnetic sheets, etc.
A device has also been developed that classifies defects by visually observing the reproduced image, but this requires a large recording capacity to record many still images.

[Means for solving problems]

The present invention has been made to solve these problems, and while sequentially storing two unit screens of still images of an object captured by a two-dimensional imaging device in a video memory, the video signal is Detects defects, drives a video recorder when detecting defects,
It is an object of the present invention to provide a surface defect inspection device which allows a video recorder to record a memory signal stored in a memory with a delay of one unit screen, thereby reducing the required recording capacity.

The surface defect inspection apparatus according to the present invention is an apparatus for optically inspecting surface defects of a moving object, and includes:
a two-dimensional imaging device for capturing a still image of the surface of the object; a means for detecting the presence or absence of a defect by inputting a video signal of the two-dimensional imaging device; and a capacity for at least two unit screens; a video memory for storing a video signal or a signal processed therefrom; a video recorder for recording the signal in the video memory; an imaging position detector for the object; means for driving a recorder; means for superimposing a signal in a video memory corresponding to a unit screen in which the presence of a defect is detected; and information on an imaging position of an object detected by the imaging position detector; and a superimposed signal. 1 after the video recorder starts driving
It is characterized by comprising means for recording with a delay of a time corresponding to a unit screen.

〔Example〕

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described in detail below based on drawings showing embodiments thereof.

FIG. 1 is a schematic block diagram showing the overall configuration of a surface defect inspection apparatus according to the present invention.

The strip 10 to be inspected is moved in its longitudinal direction, and a 2:1 interlaced TV camera 11 is placed directly above the moving area.
a and 11b are arranged, and the width direction of the strip 10 is set to 1/2 each as an imaging field of view. The video signal of the captured image is transmitted to TV camera control 1.
2a and 12b are alternately input to the image processing circuit 13 via the switcher 12.

The image processing circuit 13 includes a circuit for differentiating the video signal, and the differential signal is input to the control circuit 20 which is the control center of the imaging recording system of the apparatus of the present invention.
The signal is input to a video memory 16 having a capacity of one frame (two fields).

If the differential signal of the input video signal exceeds a predetermined threshold, the control circuit 20 determines that a defect exists in the portion corresponding to the captured image. The presence or absence of such a defect is determined on a field-by-field basis.

The stored contents of the video memory 16 are recorded by the video tape recorder 18 as will be described later, and the image position of the strip 10 by the television cameras 11a and 11b, in other words, is superimposed on the characters indicating the position of the defect. It is recorded on a recording medium, namely video tape. 17 is a superimposer for superimposing the characters and the recorded image of the video memory 16.

A signal input to the video tape recorder 18 for recording is displayed on the monitor 19, and an image reproduced by the video tape recorder 18 is also displayed on the monitor 19.

Reference numeral 14 denotes a strobe light source installed diagonally above the imaging area of the strip 10 to illuminate the imaging area of the television cameras 11a and 11b for still image capturing.The light intensity can be adjusted by adjusting the voltage applied to the strobe light source 14. Power is supplied from a strobe power source 15 that adjusts the flash.

A pulse generator 21 is disposed below the movement range of the strip 10.
The strip 10 is rotated by a touch roller that comes into contact with the strip 10, and outputs an amount of pulses corresponding to the amount of movement of the strip 10.
This output pulse is input to the control circuit 20.

22 is an editing and aggregation device using a personal computer system, which includes a computer body 22a, a monitor 22b, a keyboard 22c, a printer 22d, and a floppy disk drive 22e.
When an operator monitors the monitor 30 to evaluate defects and classify them, he inputs a symbol corresponding to the classification using the keyboard 22c.

The computer main body 22a combines the input information from the keyboard 22c and the information given from the control circuit 20, that is, the recording position information of the corresponding part on the video tape and the imaging position information of the strip 10, and outputs the input information to the floppy disk drive 22e.
The information is recorded on a floppy disk within the computer, and displayed on the monitor 22b by reproduction, or recorded on the printer 22d.

The editing and tallying device 22 tabulates each type of defect based on such input information, and displays the tally on the monitor 22b or outputs it on the printer 22d.

Next, imaging control by the control circuit 20 will be explained. The control circuit 20 issues a trigger signal for the strobe power source 15 at appropriate intervals as shown in FIG. 2A.
The strobe light source 14 is thereby driven.

The control circuit 20 provides a vertical synchronization signal to the television camera control 12a in synchronization with this trigger signal, and further provides a vertical synchronization signal to the television camera control 12b with a delay of one field. As a result, the television cameras 11a and 11b capture still images caused by the light emitted from the strobe light source 14. The light emitting time of the strobe light source is set so that it does not interfere with the imaging of one frame, and the light emitting interval is set so that it does not interfere with the inspection of the entire surface of the moving strip 10.

The control circuit 20 controls each television camera 1
During the field in which 2a and 12b output video signals, the switcher 12 is controlled to connect the television camera control 12a or 12b to the image processing circuit 13.

The image processing circuit 13 differentiates video signals of still captured images that are sequentially input from the television camera controls 12a and 12b. FIG. 2B shows this differential signal, and the defect-existing portion has a large amplitude. This differential signal is stored in the video memory 16 (FIG. 2C). Note that when this differential signal is read out and displayed on the monitor 19, it is displayed as an image in which the flaw is emphasized.

On the other hand, the differential signal is input to the control circuit 20, and 1
It is checked whether there is a portion in the differential signal of the field that exceeds a predetermined threshold value set therein. Then, as shown in the three signals on the left side of Figure 2, the threshold value [second
If there is a portion exceeding the value shown by the broken line in Figure 2), a video tape recorder activation signal VS (Figure 2D) is output between the relevant field and the next field. In response to this, the video tape recorder 18 operates for two fields. 2 TV cameras 1
If a defect exists in both the captured images 1a and 11bn, the activation signal VS will be input for two consecutive fields as shown in FIG. It operates for 3 fields. On the other hand, if a defect exists only in the image of one of the television cameras, for example 11a, it will operate for two fields and then stop, as shown in the center of FIG.

The control circuit 20 controls the read address of the video memory 16, and records the differential signal of the frozen video signal in the video memory 16 from a timing delayed by a time corresponding to one field after the start of driving of the video tape recorder 18. [Figure 2 E]. In other words, the field in which the defect exists will be recorded on the videotape with a delay of two fields in total. Also, both television cameras 11a,
If a defect is detected in the image 11b, 2 fields are recorded continuously, and in the end 3 fields are recorded on the videotape.
Two fields are consecutively recorded in the field recording space. Note that the reason why recording is not performed in the first field immediately after startup is because the running of the tape is unstable.

On the other hand, the control circuit 20 includes a pulse generator 21
Since a signal indicating the amount of movement of the strip 10 is inputted from the control circuit 20, the control circuit 20 can specify the amount of movement of the strip 10 from the start of the inspection to the time when a defect is detected, or in other words, the imaging position.

The control circuit 20 supplies this position information to the superimposer 17 to record it on a videotape.
In this way, only the defective screen will be recorded on the videotape, and if the defect is captured simultaneously by both television cameras (which is often the case), two fields will be recorded on the tape length of three fields. images will be recorded, saving storage capacity and making it easier to inspect long objects. However, conventionally, in such a case, one screen (one frame) of one television camera was recorded in three fields, so a total of six fields were required.

If the classification and location of defects are input into the personal computer system 22 as in the embodiment, the information necessary for maintenance, excision, etc. can be immediately processed and obtained.

Note that when playing back a videotape, the signal of one field is played back twice and combined into one frame for display in order to improve the image quality.

In addition, in the above embodiment, two television cameras were installed to inspect only the top surface, but if it is necessary to inspect the bottom surface as well, it is necessary to install two television cameras and a light source on the bottom side as well. , all that is required is to sequentially switch the controls for a total of four television cameras. In this case, when a screen with defects is captured simultaneously by all cameras, as is clear from the above, 4 fields of images are recorded on the tape length of 5 fields, resulting in an even higher resolution. It becomes possible to record density.

Furthermore, although a 2:1 interlaced TV camera is used in the above embodiment, a non-interlaced TV camera may be used. Needless to say, in this case, one frame = one field constitutes a unit screen. Furthermore, although the above embodiment uses two television cameras, it is also possible to use one television camera. In the case of these non-interlaced systems or even when one television camera is used, the present invention can reduce the recording capacity in that defective unit screens are recorded by a video recorder.

Further, in the above embodiment, defects were detected by analog differentiation of the video signal, but the present invention is not limited to this, and digital differentiation or other methods may be used.

Further, the signal to be stored in the video memory 16 may be the video signal itself instead of the differential signal of the video signal as described above. Which one to use depends on the state of the surface image of the inspection object, and it is preferable to record a signal that allows defects to be easily recognized during reproduction and visual inspection.

Furthermore, in order to obtain a stationary surface, the television camera 11 may be provided with a high-speed shutter instead of using the strobe light source 14 described above.

Furthermore, the means for recording the contents of the video memory is not limited to a video tape recorder, but may be other magnetic or optical media.

〔effect〕

In the case of the present invention as described above, since the recording by the video recorder is performed as a defective unit screen, there is no waste in recording. Therefore, the substantial effective recording density of the recording medium can be increased. Furthermore, since the video signal is recorded after a predetermined time delay after the video recorder is driven, there is no recording failure at the start of driving. Furthermore, the present invention has excellent effects, such as when there are consecutive images with defects, since the video recorder does not stop, there is no problem in this case.

[Brief explanation of the drawing]

Figure 1 is a schematic block diagram of the device of the present invention;
The figure is a time chart for explaining its operation. 11a, 11b...TV camera, 12...Switcher, 12a, 12b...TV camera controller, 13...Image processing circuit, 14...Strobe light source, 16...Video memory, 18...Video tape recorder, 20... ...Control circuit, 21...
...Pulse generator.

Claims (1)

[Scope of Claims] 1. An apparatus for optically inspecting a moving object for surface defects, comprising: a two-dimensional imaging device for capturing a still image of the surface of the object; and a video signal of the two-dimensional imaging device being input. means for detecting the presence or absence of a defect by using a video memory; a video memory having a capacity for at least two screen units and storing the video signal or a signal obtained by processing the video signal; and a video recorder for recording the signal in the video memory. an imaging position detector for the object; means for driving a video recorder when the presence of a defect is detected; a signal in a video memory corresponding to a unit screen in which the presence of a defect is detected; A surface characterized by comprising means for superimposing information on the imaging position of an object detected by a position detector, and means for recording the superimposed signal with a delay of one unit screen time after the start of driving of a video recorder. Defect inspection equipment. 2. The surface defect inspection apparatus according to claim 1, wherein the means for detecting the presence or absence of a defect includes a video signal differentiation circuit. 3. The surface defect inspection apparatus according to claim 1 or 2, wherein the video memory stores a differential signal of a video signal.