JPS6042674B2 - Automatic inspection range setting method for surface inspection equipment - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention captures images of the surface of an object to be inspected using a plurality of imaging devices,
The present invention relates to an automatic inspection range setting method for an apparatus that inspects the surface of an object to be inspected using the video signal.

The surface of the object to be inspected, such as a steel plate on a hot rolling line, is imaged with a television camera. If there is a flaw on the surface of the steel plate, the flaw will appear in the video signal as an amplitude change part, so the output video signal of the camera is processed. The applicant has developed a surface inspection device that detects defects by detecting amplitude changes, and has filed patent application No. 51-86387.
No. 51-87017, etc. By the way, when using a method that regards flaws as amplitude changes in a video signal, amplitude changes can be caused not only by flaws but also by steel plate edges, copper plate guides on hot rolling lines, and even horizontal synchronization signals, so these should be differentiated. Therefore, in the above-mentioned surface inspection equipment, as shown in Fig. 3, the edge detector ED detects the left and right edge signals of the copper plate, and between these edge signals, the width of the steel plate excluding both edges of the steel plate is detected. ) Generate an inspection range setting signal to make a narrow range into an inspection range using the circuit CAS, and convert this signal into a video signal Sg from a television camera TVC.
In addition to the input defect detector signal, it also acts as a mask, so that error-free and accurate flaw detection can be performed only from the video signal for the steel plate surface in the above range. By the way, in order to improve the accuracy of surface inspection and make it possible to detect even the smallest flaws, we need to use multiple cameras, especially since the steel plates used in rolling lines are wide and the resolution of television cameras is limited.
It is necessary to divide the surface of the steel plate and image each part using these cameras. In this case, the problem is the aforementioned inspection range. In other words, for example, if we consider the case where two cameras share images of each half of the width of a steel plate surface, a camera whose coverage range is from the left edge to the center can detect the left edge signal, but there is no right edge signal, and there is no signal from the center. A camera whose defense range extends to the right edge can detect the right edge signal, but not the left edge signal. The first and second inventions are intended to deal with the above problems, and include a plurality of imaging devices that divide the surface of an object to be inspected into images in the width direction, and an inspection range that is determined using an output video signal from the imaging devices. In an automatic inspection range setting method for a surface inspection apparatus that includes an inspection range setting circuit that determines an inspection range and a circuit that detects surface defects from a video signal within the inspection range, each imaging device is set so that the imaging ranges of each imaging device are adjacent to each other. After positioning, a horizontal scanning line corresponding to the setting line outside the inspection range is sampled, and a counter is activated by the output of a setting line sampling circuit that outputs a pulse corresponding to the horizontal scanning period. Or, when the right edge detection signal is input, the count value of the counter is written to the memory, and in the next horizontal scan, the value of the memory is loaded to the counter, the counter is down-counted, and the counter is output from the counter. The follow signal is input to the inspection range setting signal output circuit as a pseudo edge signal on the left or right side of the inspection range, and for parts where the imaging range is adjacent, the horizontal synchronization signal is used as an edge signal for that part to set the inspection range. In addition, in the automatic inspection range setting method of the surface inspection device, the imaging ranges of each imaging device are made to overlap, and the horizontal line corresponding to the setting line outside the inspection range is The first counter is activated by the output of the set line sampling circuit which extracts the scanning line and outputs a pulse corresponding to the horizontal scanning period, and the left or right edge detection signal of the object to be inspected is input. At this time, the count value of the first counter is written to the memory, and in the next horizontal scan, the value of the memory is loaded to the counter, the first counter is down-counted, and the follow signal output from the first counter is as a pseudo edge signal on the left or right side of the inspection range, and a second counter preset with a constant that counts down in synchronization with the first counter and indicates the inspection end point or start point.
The present invention is characterized in that the follow signal from the counter is input to the inspection range setting signal output circuit as an edge signal for a portion where the imaging ranges overlap. Regarding the longitudinal direction of the steel plate, if the frequency of imaging by the TV camera is increased, it should be possible to image the entire surface of the steel plate without omission even if it is moving at high speed with one camera, but the There is a limit to the increase in imaging frequency due to the operating frequency of the strobe device and the required signal accumulation time of the TV camera.
Therefore, it is necessary to share the image capture with a plurality of televisions. In this case (the same applies even in the case of one inspection unit), it is preferable that the inspection ranges of each inspection are close together in the longitudinal direction of the steel plate, and it is not preferable that the inspection ranges be separated or overlapped because this will lead to no detection of defects or duplicate detection. In order to make the inspection range close each time, a method is used to change the imaging frequency according to the speed of the steel plate, but it is difficult to make them completely close together. Therefore, in the present invention, the inspection range of the steel plate 1 is divided into two parts in the longitudinal direction.
The TV cameras on each stand take separate images, and the next inspection area is closely spaced or overlaps with the next inspection area, and for the overlapped area, the inspection area of one of the upper and downstream TV cameras, for example, the upstream TV camera, is restricted. Both inspection ranges were made to be close to each other. That is, the second invention of the present invention includes a plurality of imaging devices that divide images of the surface of an object to be inspected in the width direction and the direction of movement of the object to be inspected, and an inspection range setting that determines the inspection range based on the output video signal of the imaging devices. In an automatic inspection range setting method for a surface inspection device equipped with a circuit and a circuit for detecting surface defects from a video signal within the inspection range, the number of lines in one field when repeated imaging of the steel plate surface is performed without excess or deficiency is defined as LSl steel plate. It has an accumulator that accumulates Ls/NO each time the pulse is input during one field, with the number of pulses indicating the speed as NO, and a counter to which the output of the accumulator is preset, and the accumulator is inspected. Accumulation is performed before the start and preset in the counter in synchronization with the vertical synchronization signal, the counter counts down in synchronization with the horizontal synchronization signal, and the follow signal of the counter indicates the end of the inspection range in the moving direction. The present invention is characterized in that the inspection range is input as a signal to a setting signal output circuit. Next, these will be explained in detail with reference to the drawings. FIG. 1 shows an example in which the surface of an object to be inspected is inspected using four television cameras.

SP is an object to be inspected, which in this example is a steel plate on a hot rolling line.
A, B, C, and D show the imaging ranges of four high-resolution television cameras.The cameras are fixed, so the imaging range is constant, but since the steel plate SP is being transported and meandering, that is, moving laterally, each camera The surface area of the steel plate imaged by is not constant. The inspection range A-D is such that the steel plate does not come off even if the steel plate meanderes, and the imaging is repeated in this range according to the transport speed of the steel plate to ensure that the entire surface of the steel plate is completely covered. And ensure that the test can be performed without recurrence. Lines 11 and 12 indicated by chain lines are called setting lines, and the left and right edges of the steel plate are detected on these lines, and the inspection range is set based on the edges, and this is stored.
If an edge is not detected, the inspection range is set using the stored value. The methods of edge detection, inspection range setting, storage, reading, etc. are described in detail in the aforementioned Japanese Patent Application No. 51-87017. By the way, when one camera covers the entire width W of the object to be inspected, the video output of the camera includes both the left and right edges, but the first
In the mela arrangement shown in the figure, only the left or right edge is included. Figures 2 a to d show the video signals on the setting lines of the television cameras TVCa to TVCd whose imaging range is A to D, but as shown in these figures, the video signals of the left television cameras TVCa and TVCc are There is a step EL indicating the left edge, but since the scanning ends at the center of the steel plate, the right edge is not included.On the contrary, the video signals of the TV cameras TVCb and TVCd on the right have a step ER indicating the right edge. is included, but the left edge is not included because the scan starts from the center of the steel plate. Therefore, as shown in FIGS. 2E and 2F, only the left edge signal h1 can be extracted from the left camera, and only the right edge signal H2 can be extracted from the right camera. By the way, as mentioned above, the imaging range of the camera is constant, and this has nothing to do with the movement or meandering of the copper plate.

Therefore, assuming that scanning is performed from left to right, it is possible to match the end of the imaging range of the left camera with the beginning of the imaging range of the right camera. All you have to do is adjust the start and end points of the horizontal scan from which the signal is extracted. In this way, the end of the imaging range of the left camera can be simply the trailing edge of the horizontal blanking signal, and the starting point of the imaging range of the right camera can be the leading edge of the horizontal blanking signal. Of course, the front and rear edges may be advanced or delayed by a predetermined distance, and the point is that the starting and ending ends of the effective portions used for flaw detection coincide with each other. Fourth
The figure shows an example of the inspection range setting circuit for the left and right cameras.
10 is a circuit for extracting the setting line, and a vertical synchronizing signal VD
and the horizontal synchronization signal HD are input, and outputs a signal S1 that is turned on for a period equivalent to one horizontal scanning period from the nth horizontal synchronization signal (n is an arbitrary number) to the n+1st horizontal synchronization signal counting from the vertical synchronization signal. do.

This signal S1 is applied to the setting line 1 as is clear from FIG.
1,1. shows. 11 is memo I8 12 is counter, 13
are clock oscillators, which have the function of storing and reproducing edge signals as detailed in the aforementioned application.

14 is an inspection range signal sampling circuit, and CES is an inspection range setting signal output circuit, which includes an AND gate 16 and a flip-flop circuit FF.

FIG. 4a shows an inspection range setting circuit for the left camera, and FIG. 4b shows an inspection range setting circuit for the right camera. To summarize this with reference to FIG. 5, FIG. 5 1 shows the horizontal blanking signal 1 (BL),
2 and 6 indicate left and right edge signals H1 and h2.

As shown in Figure 2, the edge signal has a very large change in the amplitude of the video signal at the edge, so the differential value is determined and thresholded, and the previously expected edge is left and the other parts are masked. It can be detected by passing it through a gate.
The setting line signal S1 is as shown in FIG.
2, sets the counter 12 as an up counter, and starts counting the clock CLK from the clock oscillator 13. From the video signal, the left edge signal h
When 1 is detected, this signal is applied to the AND gate 15, which outputs a signal S2 as shown in FIG. let The count value indicates the length from the start end to the edge of horizontal scanning. In the next horizontal scan, the setting line signal S1 is 0, the counter 12 is set to a down counter by the signal S1, the contents of the memory 11 are loaded by the horizontal synchronization signal, and the clock CLK is counted (subtracted). Start. When the contents of the counter reach 0, a follow signal S3 is generated, which is passed through an AND gate 16 to a pseudo left edge signal S4.
input to the flip-flop lower F and set it. The flip-flop is reset by the horizontal synchronization signal D and produces the inspection range setting signal Sa for the video signal of the left camera shown in FIG. For setting the inspection range for the video signal of the right camera, the circuit shown in FIG. 4b is used, and the right edge signal H2 is input to the AND gate 15. When the set line sampling circuit 10 outputs the set line signal S1, the counter 12 is also set to an up counter, and the clock C
Start counting LK. When the right edge signal H2 appears, the AND gate 15 outputs the signal S2 as shown in FIG.
is output, and the count value of counter 12 at that time is stored in memory 1.
Store it in 1. This count value indicates the length from the starting edge of horizontal scanning to the right edge. In the next horizontal scan, the signal S1 is O, the counter 12 is set to a down counter, and when the horizontal synchronizing pulse HD is input, the counter 12 is loaded with the contents of the memory 11 and counts (subtracts) the clock CLK. Start. counter 12
When the content of becomes O, the follow signal S3 is outputted, passes through the AND gate 16, becomes the right pseudo edge signal S5, and is input to the lower flip-flop F. The flip-flop is set by the horizontal synchronizing signal HD and reset by the signal S5 to produce the inspection range setting signal Sb for the video signal of the right camera shown in FIG. In this way, the inspection range is set based on the steel plate edge signal detected on the setting line and stored, and the stored value is used on the same screen, and the stored value is updated every time the screen changes.

Since the inspection range setting signal is not required during a period when surface inspection is not performed, such as a vertical blanking period, the inspection range signal sampling circuit 14 sets the output signal S6 applied to the AND gate 16 to "°0" during the period. to close the gate.Next, referring to Fig. 6, move the steel plate in the longitudinal direction (transfer direction).
The imaging range setting will be explained below.

In this figure, the same parts as in FIG. 4 are given the same reference numerals and perform the same operations. The inspection range sampling signal circuit 14 and its gate circuit 16 shown in FIG. 4 are not shown in this figure, and a counter 17 is provided instead. This counter 17 sets the right end of the left camera and the left end of the right camera inspection range. That is, set the numerical value C necessary for setting the left and right end inspection ranges in the counter, and set the clock CLK with the horizontal synchronization signal book.
Start counting (subtraction). For example, in the case of the left camera, the left pseudo edge signal S3 force counter 1 is
Since the follow output signal S7 of the counter 17 is O, the inhibit gate 18 at this time outputs from ゜゜1.
``Produces an output. The signal S3 is inverted by the inverter 20 and then applied to the enable terminal of the counter 12, so the counter stops counting, and the signal S3 and therefore the output signal S8 of the gate 18 maintains the state of "゜1゛."The counter 17 performs subtraction. continues, and when the set number C is finally subtracted, the contents of the counter 17 become 0. At this time, a follow signal S7 of ゜'F゛ is generated, the gate 18 is closed, and the counting of the counter 17 is stopped in the same way. Therefore, the output signal S8 of the gate 18 becomes an inspection range setting signal for the left camera.
In order to use the output signal of the gate 18 for the right camera, the set value C of the counter 17 may be changed. To explain this point in detail using FIG. 7, this example is based on the assumption that the left and right imaging ranges overlap as shown in the figure. Here, the boundary between the left and right inspection areas is assumed to be at the position of the dotted line AN.
Regarding the inspection area on the left side, the counter output S3 is 0 from when the horizontal synchronizing signal HD (1) is input until the left age signal h1 (2) is input, and when h1 is input, the follow signal S3 is output. (3). This follow signal S3 enables the counter 12, so the next H
The level "1" is maintained until D is input. On the other hand, counter 1
7, a count value C corresponding to the width direction indicated by the dotted line A-A'' is preset from the left end LE, and is counted down until the follow signal is output.Soon, the follow signal S7 is output and the AND gate 18 It is inverted and input into the AND gate 18, where S3 and I are input as S8.
Output. This S8 indicates an area from the left end edge of the object to be inspected to a predetermined right end. Next, referring to the right inspection area, the inspection area extends from a portion C'' inside the right imaging area to the right edge portion of the object to be inspected.

In the case of the right side 4 as well, the follow signal S3 is output when the edge signal H2 is input (9). Then, when a value corresponding to the inspection range shown in the figure is preset in the counter 17 as C'', the follow signal S7 is outputted at the timing shown in FIG. 7 and 10.The AND gate 18 inverts S3 in this case. 7 and 11 as the output S8.
The signal S″8=100.・S7 is output. This indicates the inspection range on the right side. Therefore, for the right camera, all you need to do is change C and change the gate configuration. Cameras TVCa, TVC on the downstream side in the steel plate moving direction F
The inspection range in the width direction is set for b, and the inspection range in the direction of steel plate movement is not limited for these cameras.

This restriction is applied to the upstream camera TVCc,
This is for TVCd. Note that the width direction inspection range setting for these downstream cameras is the same as that for the upstream camera. The steel plate moving direction inspection range limit is determined by the adders 21 and 7.
The memory 22, counter 23, setting field extraction circuit 26, etc. perform this processing. B. The number of lines (horizontal scanning lines) in one field when repetitive imaging of the copper plate surface is performed with the cameras TVCa to TVCd without excess or deficiency. ．． #l If the number of pulses PGP indicating the plate speed is NO, and the number of one field line that is just over or under when the number of steel plate speed pulses is N is x, then there is a relationship of x = LS - N / NO, so the ratio /NO=
B is set in the adder 21, and one arbitrary field period''
A signal S9 which becomes R5 is outputted by the setting field extraction circuit 26 and added to the AND gate 24, and the steel plate speed pulse PGP is inputted to the adder 21 through the gate. This adder 21 adds the contents of the memory 22 and a constant B each time the pulse PGP is input, and stores the result in the memory 22.
Write to 2. In this way, when N speed pulses PGP are input, the contents of the memory 22 become BN, that is, x. The contents X of this memory 22 are loaded into the counter 23 every time the vertical synchronizing signal VD is input, and the counter counts (subtracts) the horizontal synchronizing signal HD. When the subtraction progresses and the contents of the counter 23 become 0, the follow signal SlO
becomes “゜1゛” and closes the inhibit gate 19 which had been open until then. Also, this signal SlO is applied to the inverter 2.
5, and the counter 23 stops counting. As a result, the gate 19 is closed and the inspection range setting signal Sll is no longer output even when the next horizontal scan starts, thus limiting the inspection range in the direction of copper plate movement. The output signal of this gate 19 is used for setting the inspection range of the upstream camera. Note that in this example, the inspection range is limited only to the upstream camera.
This is because this is usually enough to prevent duplication of the inspection range.

In this way, the inspection starting point becomes the first horizontal scanning line of the downstream camera and can be made constant. As described in detail above, according to the present invention, it is possible to image the surface of an object to be inspected without excess or deficiency using a plurality of imaging devices, and to perform accurate surface inspection with high resolution.

[Brief explanation of the drawing]

Fig. 1 is an explanatory diagram showing an example of imaging an object to be inspected with four television cameras, Fig. 2 a-f is an explanatory diagram of a video signal and a flaw signal, and Fig. 3 is an overview of an already proposed surface inspection device. 4 and 6 are block diagrams showing embodiments of the present invention, and FIGS. 5 1 to 8 are waveform diagrams for explaining the operation of FIG. 4,
FIG. 7 is an explanatory diagram of the operation of FIG. 6. In the drawings, SP is the surface of the object to be inspected, TVCa to TVCd are imaging devices, CAS is an inspection range setting circuit, and AD is a defect detector.

Claims (1)

[Scope of Claims] 1. A plurality of imaging devices that divide and image the surface of an object to be inspected in the width direction, an inspection range setting circuit that determines an inspection range based on the output video signal of the imaging devices, and a video signal within the inspection range. In an automatic inspection range setting method for a surface inspection device equipped with a circuit that detects surface defects from signals, each imaging device is positioned so that the imaging range of each imaging device is adjacent to each other, and the setting line outside the inspection range is handled. A counter is activated by the output of a set line sampling circuit which extracts a horizontal scanning line and outputs a pulse corresponding to the horizontal scanning period, and when a left or right edge detection signal of the object to be inspected is input, the counter is activated. The count value of is written to the memory, and in the next horizontal scan, the value of the memory is loaded into the counter, the counter is down-counted, and the follow signal output from the counter is used as a pseudo edge on the left or right of the inspection range. A surface inspection characterized in that a signal is input to an inspection range setting signal output circuit, and for a portion where the imaging range is adjacent, a horizontal synchronization signal is input to the inspection range setting signal output circuit as an edge signal for the portion. Automatic inspection range setting method for equipment. 2. A plurality of imaging devices that divide and image the surface of the object to be inspected in the width direction and in the direction of movement of the object to be inspected, an inspection range setting circuit that determines an inspection range based on the output video signal of the imaging devices, and a video signal within the inspection range. In an automatic inspection range setting method for surface inspection equipment equipped with a circuit that detects surface defects from signals,
An accumulator that accumulates L_s/N_o each time the pulse is input during one field, assuming that the number of lines in one field is L_s and the number of pulses indicating the speed of the steel plate is N_o when repetitive imaging of the steel plate surface is performed without excess or deficiency. and a counter to which the output of the accumulator is preset, the accumulator performs accumulation before starting the test and presets the counter in synchronization with a vertical synchronization signal, and the counter is synchronized with a horizontal synchronization signal. An automatic inspection range setting method for a surface inspection apparatus, characterized in that a follow signal of the counter is inputted to the inspection range setting signal output circuit as a signal indicating the end of the inspection range in the moving direction. 3. A plurality of imaging devices that divide and image the surface of the object to be inspected in the width direction, an inspection range setting circuit that determines an inspection range based on the output video signal of the imaging device, and detects surface defects from the video signal within the inspection range. In the automatic inspection range setting method of a surface inspection device equipped with a circuit, the imaging ranges of each imaging device are made to overlap, the horizontal scanning line corresponding to the set line outside the inspection range is extracted, and the pulse corresponding to the horizontal scanning period is extracted. The first counter is activated by the output of the set line extraction circuit that outputs the set line, and when the left or right edge detection signal of the object to be inspected is input, the count value of the first counter is written to the memory, and from the next time onwards. In horizontal scanning, the value of the memory is loaded into the counter, the first counter is counted down, and the follow signal output from the first counter is used as a pseudo edge signal on the left or right side of the inspection range, and the first counter is counted down. The second counter is preset with a constant that counts down in synchronization with the first counter and indicates the end or start point of the test.
An automatic inspection range determination method for a surface inspection apparatus, characterized in that a follow signal from a counter is input to an inspection range setting signal output circuit as an edge signal for a portion where imaging ranges overlap.