JPS5847016B2 - Self-diagnosis method for surface inspection equipment - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a self-diagnosis method for testing whether a surface inspection device is normal or abnormal.

Surface flaws on an object to be inspected, such as a rolled steel plate, are of course undesirable, and depending on the degree, they can make the product defective.

Each flaw is caused by a specific cause, and if the cause of the flaw is not detected early and the cause of the flaw is removed, a large number of products with the same type of flaw will occur, all of which will become defective, resulting in large economic losses. may be given.

Therefore, various surface flaw inspection devices have been developed and put into practice.

The present applicant filed Japanese Patent Application No. 51-86387 (Japanese Patent Publication No. 57-35
The surface inspection device proposed in No. 788) is one such device, which irradiates a strip-shaped object moving at high speed with a strobe, captures a still image of the surface with a high-resolution television camera, and then records the image from the camera. Sends the signal to the memory and flaw detection circuit.

The memory is equipped with a plurality of recorders that store image signals for each screen, and the image signals from the camera are sequentially written, then reproduced, and then erased, and these processes are repeated with a one-timing shift from each other.

When a flaw detection signal is output from the flaw detection circuit, an image signal of one screen or only the flaw portion of the screen corresponding to the flaw signal is inputted to one of the second recorder group, and the second recorder Then, the image signal is outputted to a monitor device for a suitably set time, thereby displaying the surface of the object to be inspected that has a flaw.

The operator visually inspects this image, performs a flaw inspection, records the
Take appropriate measures such as warning.

A device of the same kind was proposed by the applicant in Japanese Patent Application No. 51-87017 (
Special Publication No. 55-41077), Patent Application No. 51-87011
(Special Publication No. 57-24503), etc.

By the way, surface inspection equipment is installed at strip mills and other strip manufacturing sites, and is often operated in harsh environments such as high temperature, high humidity, and dust, so it is necessary to constantly monitor whether the equipment is operating properly. It is desirable to do so.

On the other hand, as shown in Figure 1, the tip and tail ends of manufactured strips are deformed and cannot be used as products, and the positions of these ends on the production line are often unstable. The flaw inspection is not carried out at the end, but is carried out from ST2, which is a certain length from the tip ST1 of the strip ST, and the same is usually done at the tail end as well.

The present invention focuses on this point, and performs surface imaging and analysis including both side edges of the strip even during the preparation period of length L, and determines whether the surface inspection device is normal or abnormal depending on whether the side edges are detected. This is what we are trying to judge.

According to this method, it is possible to easily self-diagnose the normality or abnormality of the inspection device by using the idle period of the inspection device each time the surface inspection of each strip material is performed and before the start of the inspection, and it is highly reliable. Surface inspection can be performed.

The present invention provides a light source that instantaneously illuminates the surface of a moving object to be inspected;
A television camera that captures a still image of the surface of the object to be inspected; a circuit that outputs an inspection range setting signal from the image signal output from the camera; a defect detection circuit that outputs a detection signal including a signal, and a circuit that generates a timing signal that starts a surface inspection using the inspection range setting signal and the detection signal after a preparation period corresponding to a predetermined length range from the tip of the object to be inspected. In the self-diagnosis method for a surface inspection device, the presence or absence of a detection signal including a signal of the flaw is inspected according to the presence or absence of an edge and flaw in the defect detection circuit during the preparation period, and when there is no detection signal, the surface The present invention is characterized in that it provides a warning of an abnormality in the inspection device, which will be described in detail below with reference to embodiments.

FIG. 2 shows an embodiment of the present invention, where ST is a strip-shaped object to be inspected such as a hot-rolled strip, LS is a light source such as a strobe device that instantaneously illuminates the surface of the object to be inspected, and CM is the surface of the object to be inspected. FS is a sensor that detects the tip of the object to be inspected.

Also, ED is an edge detection circuit, FD is a defect detection circuit, WS is a circuit that automatically sets the inspection status, TG is a detection start timing generation circuit, AG is an alarm generation circuit, 01 to G
5 is a gate circuit, and Fl is a flip-flop circuit.

Appropriate circuits may be used for edge detection, defect detection, and automatic width setting circuits.
A preferred example is the circuit described in the section entitled "Automatic Detection Range Setting Circuit".

This existing proposal is detailed in the specification of the above-mentioned application, and its outline is as follows.

As shown in FIG. 3g, the image signal Sg from the television camera commercial consists of a horizontal synchronizing signal Syn, an image signal S1 of the surface of the object to be inspected, an image signal S2 of its surroundings, and a flaw signal N included as the case may be. .

Since what is desired is the flaw signal N, the signal Sg is differentiated and then full-wave rectified to obtain the signal shown in Figure 3. In this way, a flaw signal N can be obtained from the gate as shown in FIG. 3N.

The circuit that performs this operation is as shown in Figure 4, in which CM is the television camera, 1 is a differential circuit, 2 is a full-wave rectifier circuit, and 3 is a circuit that calculates the period T from the edge of the object to be inspected. 4 is an AND gate.

Differentiator circuit 1 and full-wave rectifier circuit 2 correspond to defect detection circuit FD in FIG. 2, and edge detection and inspection range T setting circuit 3 corresponds to edge detection circuit ED and automatic width setting circuit WS in FIG. .

Edge detection is performed by taking advantage of the fact that, as shown in Figure 3 Sg, the level of the image signal on the surface of the object to be inspected differs significantly from that around it, and that this is more sensitive than level changes caused by flaws or synchronization signals. The period T, which is narrower than the width W, can be determined by signal processing such as slightly delaying the width detection (edge detection) signal and the image signal.

FIG. 5 shows an example, in which 3a is a distributor, 3b and 3c are delay circuits with the same delay time τ, 3d is a differential amplifier, 3
e is a Schmitt circuit, and 3f is a flip-flop.

The image signal Sg of the television camera CM is directly applied by the distributor 3a to one input terminal of the differential amplifier 3d via the delay circuit 3b, and to the other input terminal of the differential amplifier 3d on the other hand.

FIG. 6 Sg shows the image signal Sg, and FIGS. 6 e and f show the waveforms of the delayed signal e and the direct signal f of the signal Sg applied to the amplifier 3d.

The signal e is a signal obtained by simply delaying the signal Sg by a fixed time τ, but the signal f is affected by the reflected wave after 2゛τ because the delay line 3c with one end open is connected to this signal input circuit. As shown in the figure, there are two stages of rising and falling parts.

When the amplifier 3d takes the difference between these signals e and f, the result is a signal g with the waveform shown in FIG. The signal shown in Figure 6 is obtained.

As shown in the figure, this signal corresponds to the edge of the object to be inspected, but the signal at the beginning is delayed by the delay time τ, so the pulse interval of the signal indicating both edges is τ than the width W of the object to be inspected. Only narrow.

By setting and resetting the flip-flop using this signal, a signal C indicating the inspection range T shown in FIG. 6C is obtained from the circuit 3f.

Next, to explain the operation of the circuit shown in Fig. 2, as mentioned above, the light source LS instantaneously illuminates the surface of the object to be inspected moving at high speed, and the television camera captures a still image of the surface and outputs an image signal Sg. do.

The signal Sg is converted by the defect detection circuit FD into a signal including the synchronization signal Syn, edge signal S3, and flaw signal N shown in FIG. 3, and this signal S5 is applied to the first input terminal of the AND gate G1.

Note that this signal S5 is delayed by τ/2, for example, and the inspection range T
Make sure that it completely enters the inside of the test object.

The image signal Sg is also applied to the edge detection circuit ED and the automatic width setting circuit WS, and these circuits output a signal indicating the inspection range T, which is applied to the second input terminal of the AND gate G1.

As a result, the flaw signal N is outputted from the gate G1 in the manner shown in FIG. It will start from where you enter.

That is, the tip detection sensor FS detects the tip ST1 of the inspected material by photoelectric or other means, and this tip detection signal S6 is applied to the detection start timing generation circuit TG, which generates a signal S7 delayed by a time corresponding to the length L. The signal S7 is input to the AND gate G1 to open it.

The above are the main parts of the previously proposed surface inspection apparatus, but in the present invention, gate G2. G3. G, , G6, flip-flop F1 and alarm generating circuit AG are added.

Gate G2. G3 is an inhibit gate, and one input terminal of the AND gate is an inverter.

The gate G3 receives the tip detection signal S6 at one input terminal,
The other inverting input terminal receives the signal S7.

Therefore, the output of the gate G3 is "1" for a period of length L;
Thereafter, a signal S8 which becomes "OF+" is generated.

This signal S8 is applied to one input of an AND gate G, and the signal S5 and blanking signal S9 are input to the other input of the gate.

Therefore, the gate G5 is opened during a period of length L to pass the signal S5, and if the light source LS, television camera CM,
If the defect detection circuit FD, the tip detection sensor, the detection start timing generation circuit TG, etc. are normal, the signal S5 always includes at least the edge signal S3 with a large amplitude. The output signal SIO stored in F1 inhibits gate G2.

Therefore, there is no output from the gate G2 and the alarm generating circuit AG does not operate.

On the other hand, if there is no output from the defect detection circuit FD, the gate G
2 is not inhibited, so gate G2 is S
After T, an output is generated and the alarm generating circuit AG is activated.

The fact that there is no output signal S5 of the defect detection circuit FD is clearly abnormal, that is, the light source LS, television camera CM
, or defect detection circuit FD, and the operator immediately takes appropriate measures in response to the alarm.

As described in detail above, according to the present invention, the normality and abnormality of the surface inspection device can be determined by using the non-inspection part at the end of the object to be inspected without interfering with the surface inspection such as by stopping the surface inspection. Each unit can be inspected each time.

Note that for objects to be inspected that do not have non-inspection portions, a portion similar to the non-inspection portion may be provided.In this case, there is a problem that the inspection area becomes shorter, but if the length of the object to be inspected is long, In this case, this is not a particular problem.

[Brief explanation of the drawing]

FIG. 1 is an explanatory diagram of an example of an object to be inspected, FIG. 2 is a block diagram showing an embodiment of the present invention, FIGS. 4 and 5 are block diagrams showing details of each part of FIG. 2, and FIG. and FIG. 6 is an explanatory diagram of the operation of FIGS. 4 and 5. In the drawings, ST is an object to be inspected, LS is a light source, CM is a television camera, ED and WS are inspection range setting signal output circuits, FD is a defect detection circuit, TG is a timing signal generation circuit, and AG is an alarm generation circuit.

Claims (1)

[Claims] 1. A light source that instantaneously illuminates the surface of a moving object to be inspected, a television camera that captures a still image of the surface of the object to be inspected, a circuit that outputs an inspection range setting signal from the output image signal of the camera,
a defect detection circuit that outputs a detection signal including a flaw signal according to the edge of the object to be inspected and the presence or absence of a flaw from the image signal; and the inspection after a preparation period corresponding to a predetermined length from the tip of the object to be inspected. In the self-diagnosis method for a surface inspection apparatus, which includes a circuit that generates a timing signal for starting a surface inspection using a range setting signal and the detection signal, the defect detection circuit detects an edge of the defect detection circuit during the preparation period according to the presence or absence of the defect. 1. A self-diagnosis method for a surface inspection device, the method comprising: inspecting for the presence or absence of a detection signal including a signal, and issuing an alarm for an abnormality in the surface inspection device when the detection signal is absent.