JP3413307B2 - Surface inspection equipment - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a surface inspection device for photoelectrically detecting a defective portion existing on the surface of an object to be inspected, such as a continuously running web.

[0002]

2. Description of the Related Art Various surface inspection devices are known for detecting defects existing on the surface of a continuously running sheet-like object such as a film, a paper, and a thin metal plate. Product quality control is performed. Among these surface inspection devices, a device that scans the surface of the inspection object with inspection light such as laser light, receives reflected light or transmitted light with a light receiver, and evaluates the presence or absence of surface defects by the photoelectric signal output is Since it can be inspected without contact and at high speed, it has been widely used in production lines.

As such a photoelectric type surface inspection device, for example, Japanese Examined Patent Publication No. 56-31737 and Japanese Patent Laid-Open No. 4-31737 are disclosed.
The one described in Japanese Patent No. 125455 is known. In the device described in the former publication, the inspection light is scanned from the central portion side to the end portion side at the end of the inspected object to eliminate the dead zone due to the rising response of the light receiver, and The inspection can be performed up to the part position. Also,
The inspection device described in the latter publication uses a light-shielding plate that scans the inspection light from the end side to the center side of the inspection object and moves in the width direction following the meandering of the inspection object. . Then, one edge of the shading plate is made to coincide with the end position of the object to be inspected, and the inspection light is cut in the scanning area before reaching the end part of the object to be inspected. The inspection is started from the moment when the scanning position is exceeded.

[0004]

[Problems to be Solved by the Invention]
In the surface inspection apparatus described in Japanese Patent Publication No. 31737-, although the dead zone due to the delay of the rising characteristic of the light receiver is certainly eliminated, when the object to be inspected meanders and the position of the end changes, When the photoelectric signal changes, it is not possible to determine whether this change was obtained before reaching the end of the inspected object or after the end was reached. Therefore, after all, there is no choice but to decide the standard inspection width based on the state that there is no meandering, and if there is a meandering that the end part of the inspected object deviates from this standard inspection width, A dead zone is unavoidably generated, and the defect position in the width direction is accompanied by a measurement error corresponding to the meandering.

On the other hand, the surface inspection apparatus disclosed in Japanese Patent Laid-Open No. 4-125455 is excellent in that the start position of the inspection is changed according to the meandering amount of the inspection object, but the scanning position of the inspection light is the light shielding plate. Since the light receiving signal rises from the moment when the edge of the above is crossed, there is a drawback that the dead zone due to the response delay of the light receiver cannot be eliminated.

The present invention has been made in order to solve the drawbacks of the prior art, and even if the inspection object is meandered, almost no dead zone is generated near the end of the inspection object. It is an object of the present invention to provide a surface inspection device capable of performing an inspection.

[0007]

In order to achieve the above object, the present invention achieves the above object, even if a meandering occurs when the test object is continuously run, the change in the end position of the test object due to the meandering causes a change in the test light. Paying attention to the fact that it is much gentler than the scanning speed, and by utilizing the edge signal obtained from the edge of the inspected object for the next inspection every time the inspection light is scanned, the dead zone near the edge is eliminated. I try to almost eliminate it. Therefore, in the present invention, in the scanning mechanism in which the end portion in the width direction of the object to be inspected is the inspection region, the inspection light is scanned from the central portion of the object to be inspected toward the end portion, and corresponding to this scanning mechanism An end signal when the inspection light scans the end of the inspected object is extracted from the photoelectric signal obtained from the light receiver provided. Then, the effective inspection period in the inspection region by the next scanning of the inspection light is determined based on the timing of extracting the end signal.

In order to accurately extract the end signal from the photoelectric signal, the photodetector detects the passage of the inspection light immediately before the inspection light from the scanning mechanism scans the inspection area. After a certain period of time, the end signal extraction operation is started. The value of this fixed time is preferably set to a value immediately before the inspection light passes through the end of the inspected object, considering that the inspected object meanders. Further, it is convenient to set the effective inspection period to a constant period between the extraction timing of the end signal and the elapse of a constant start time and a constant stop time.

When the photoelectric signal includes a defect signal, in order to specify the position of the defect portion in the width direction of the object to be inspected, the inspection light is scanned for those including the end portion in the inspection area. The position and the extraction timing of the end signal may be referred to. Further, when a scanning mechanism and a photodetector that do not include the end of the inspected object are used, one end side of the photodetector is blocked by a light shielding plate, and the light shielding plate follows the meandering of the inspected object. Then, if you move it in the width direction of the inspected object,
By using the signal obtained at the moment when the inspection light scans the edge of the shading plate in the same manner as the edge signal, even if the edge is not included in the inspection area, the defect position can be accurately determined in consideration of meandering. You will be able to identify.

In FIG. 1 schematically showing a surface inspection apparatus using the present invention, a web 2 to be surface-inspected is run at a constant speed from the lower side to the upper side in the figure by a well-known transport mechanism. Three scanning mechanisms 3, 4, 5 are provided along the width direction of the web 2. As shown for the scanning mechanism 3, these scanning mechanisms 3, 4, and 5 each include a laser oscillator 3a, a lens system 3b, a polygon mirror (rotating polygon mirror) 3c, and a photodetector 3d. The surface of the substrate is irradiated with inspection light for scanning in the width direction.

Optical receivers 6, 7, and 8 are provided corresponding to the respective scanning mechanisms 3, 4, and 5. These receivers 6,
The scanning mechanisms 7, 4 and 5 irradiate the web 2 with the scanning mechanisms 3, 4, and 5 receive the inspection light reflected on the surface of the web 2 for each scanning period, and output photoelectric signals corresponding to the received light amount. As shown in the figure, the scanning mechanisms 3, 4, 5 and the light receivers 6, 7, 8 respectively make a pair, and an inspection area including the right end portion of the web 2, an inspection area in the central portion of the web 2, and the web 2 Covers the inspection area including the left end of the. In addition, the scanning ranges of the scanning mechanisms 3, 4, 5 and the light receiver 6, so that the adjacent inspection areas overlap each other.
Lengths of 7 and 8 are fixed.

The inspection area in the central portion of the web by the scanning mechanism 4 and the light receiver 7 is set to be staggered with respect to other inspection areas by shifting in the traveling direction of the web 2, but is output from the light receiver 7. By adjusting the output timing of the photoelectric signal to be generated or the defect signal obtained by processing the photoelectric signal based on the length measurement pulse obtained from the transport mechanism of the web 2, the respective inspection areas are aligned in the traveling direction of the web 2. Can be made.

An edge position detector 10 is provided at the left edge of the web 2.
Is provided. The end position detector 10 photoelectrically monitors the position of the left end of the web 2, operates the light shielding plate moving mechanism 11 according to the amount of movement of the left end, and moves the light shielding plate 12 in the width direction of the web 2. Let As a result, when the web 2 is meandered, the light shielding plate 12 moves according to the amount of the meandering, and the right edge 12a of the light shielding plate 12 is always kept at a constant position from the left end of the web 2. Even when the web 2 meanders to the leftmost side in the figure, the light shield plate 12 has its right edge 12a.
Is long enough to partially cover the left side of the light receiver 7.

The scanning mechanisms 3 and 4 scan the inspection light from the left side to the right side of the web 2, and the scanning mechanism 5 scans the inspection light from the right side to the left side. This is because for the light receivers 6 and 8 including the end portion of the web 2 in the inspection area, a signal obtained from the end portion of the web 2 is detected without being influenced by the rising response. Further, regarding the light receiver 7 having only the central portion as the inspection area, the moment when the inspection light passes through the right edge 12a of the light shielding plate 12 can be used as a reference timing for scanning in this inspection area. .

As the inspection light is scanned, each light receiver 6,
From 7, 8 photoelectric signals 14a, 14
b and 14c are output. As can be seen from the waveform diagrams of the respective photoelectric signals, the light receivers 6, 7, 8 immediately after the inspection light is incident
The output from the device has a slow rising due to the response delay of the light receiver. However, as described above, since the adjacent inspection areas are overlapped with each other, the dead zone (inspection inadequate area) due to the response delay of the light receiver can be eliminated.

The photoelectric signal from the light receiver 6 having the right end portion of the web 2 as the inspection area is input to the defect detection circuit 20 having an edge detection function. Similarly, the defect detection circuit 20 having the same configuration is connected to the light receiver 8 including the left end portion of the web 2 in the inspection area. The photoelectric signal A of the photodetector 6 is branched into a defect signal detection channel and an end signal detection channel, and then input to a defect detection bandpass filter 21 and an end detection bandpass filter 22, respectively, and a low frequency component is It becomes a signal of a predetermined band that has been cut. In the defect signal detection channel, the signal from the defect detection bandpass filter 21 is binarized by the binarization circuit 24, and the inspection signal J
Is input to the AND circuit 25. The inspection signal J includes a low level normal signal and a high level defect signal.

In the edge signal detection channel, the signal from the edge detection bandpass filter 22 is sent to the comparator 26.
Is compared with the reference voltage, and when this is less than or equal to the reference voltage, the end portion candidate signal D is output from the comparator 26. This reference voltage is set to a level at which it can be detected that the inspection light reflected from the surface of the web 2 is no longer incident on the light receiver 6. The output terminal of the comparator 26 is connected to the reset terminal of the flip-flop circuit (FF circuit) 27, and the set terminal of the FF circuit 27 is connected to the output terminal of the timer circuit 28. The FF circuit 27 is set when the timer circuit 28 outputs the edge detection permission signal E.

The timer circuit 28 measures a predetermined time Ts from the time when the photodetector 3d incorporated in the scanning mechanism 3 outputs the detection signal B of the inspection light, and at the end of the time measurement, the end detection permission signal E is sent. Output. Even when the web 2 meanders to the left side in the drawing and the right end portion is closest to the left side, the inspection light from the scanning mechanism 3 is used for this fixed time Ts.
It is set as the elapsed time after being detected at d and immediately before passing through the right end portion of the web 2. Then, the FF circuit 27 is caused by the end detection permission signal E from the timer circuit 28.
After being set, the FF circuit 27 is reset when the end candidate signal D is input from the comparator 26, and the inverted signal F is output at the same time as this reset.

A pulse generation circuit (OS circuit) 30 composed of a one-shot multivibrator is connected to the FF circuit 27. The OS circuit 30 outputs the end signal G at the moment when the inverted signal F from the FF circuit 27 is received. The end signal G is input to the inspection width setting circuit 31. The inspection width setting circuit 31 generates an inspection width signal I that rises to a high level after a lapse of a constant start time T1 from the time of inputting the end signal G and further decreases to a low level after a lapse of a constant stop time T2, and outputs the inspection width signal I. Input to the AND circuit 25. As described above, the inspection signal J input to one terminal of the AND circuit 25 includes the low-level normal signal and the high-level defective signal. As a result, the AND circuit 25 has the high-level inspection width. The defect signal K is output only while the signal I is being input.

The photoelectric signal from the photodetector 7 having the central portion of the web 2 as the inspection region is basically the above-mentioned defect detection circuit 20 excluding the end signal detection channel,
From the moment when the light passes through the right edge 12a of the light shielding plate 12, the inspection signal is obtained along with the scanning of the inspection light. The light-shielding plate 12 follows the meandering of the web 2 and shields the left side of the light receiver 7. Therefore, the scanning position of the inspection light (rotation of the polygon mirror) is set with the instant when the photoelectric signal from the light receiver 7 rises as the reference timing. Web 2 by contrasting (corresponding to position)
The position in the width direction of can be specified. Further, when the photoelectric signals from the light receivers 6 and 8 include a defect signal, the position of the defect can be specified with reference to the timing when each end signal is extracted. It should be noted that in the region where the rise response of the photodetectors 6, 7 and 8 is poor, it can be complemented by the output from another adjacent photodetector, so the inspection sensitivity does not deteriorate in this region.

The operation of the surface inspection device is as follows. The web 2 having a constant width is set on the conveyance mechanism at the reference position in the width direction, and the traveling is started continuously. With this,
The scanning mechanisms 3, 4 and 5 are simultaneously driven to scan the web 2 with the inspection light. Web 2 for each of the light receivers 6, 7, and 8
The inspection light reflected by is incident, and photoelectric signals 14a, 14b, 14c corresponding to the received light amount are output. Web 2
If there is no defect in each, after each photoelectric signal rises due to the incidence of the inspection light on the photodetector, the photoelectric signal keeps a substantially flat waveform with the scanning of the inspection light, the end of one scanning,
Alternatively, when the scanning light passes through the edge of the web 2, the scanning light falls to the base level.

When the web 2 has a minute bright defect, as shown in the photoelectric signal 14a in FIG. 1, a bright defect pulse P1 protruding in a spike shape on the plus side appears in the flat portion of the photoelectric signal. . On the contrary, when the web 2 has a dark defect, the dark defect pulse P2 protruding to the minus side appears. Of course, if there are defects in other inspection areas,
These defect pulses also appear for the other photoelectric signals 14b and 14c.

Even if the web 2 meanders, the light shielding plate 12
The timing at which the photoelectric signal 14b from the light receiver 7 rises due to the action of is always coincident with the timing at which the inspection light from the scanning mechanism 4 scans the position at a certain distance from the left end of the web 2, so that the photoelectric signal 14b By using the rising timing as a reference, the existence position of the defect in the width direction of the web 2 can be determined from the generation timing of the defect pulse appearing in the photoelectric signal 14b and further the generation timing of the defect pulse appearing in the photoelectric signals 14a and 14b. It can be grasped accurately. In addition, photoelectric signals 14a, 14
As for the parts of b and 14c with poor rising response,
Accurate detection can be performed by using photoelectric signals from the photodetectors adjacent to each other.

FIG. 2 is a timing chart showing the operation of the defect detection circuit 20 which processes the photoelectric signal from the light receiver 6, and shows the signal waveform of each portion during the scanning mechanism 3 scans the inspection light three times. Since the present invention performs a normal operation after detecting the right end of the web 2 by the previous scan, the first scan will be described as a scan for detecting the right end of the web 2.

Immediately before the inspection light scans the web 2 by the rotation of the polygon mirror 3a, the photodetector 3d detects the inspection light and inputs the detection signal B to the timer circuit 28. As a result, the timer circuit 28 starts counting the fixed time Ts. During the period in which the fixed time Ts is measured, the FF circuit 2
Since the end detection permission signal E input to the set input terminal 7 of 7 remains at the low level, the FF circuit 27 is in the reset state and the output terminal remains at the high level.

When the time measurement of the fixed time Ts is completed, the edge detection permission signal E from the timer circuit 28 rises in a pulse shape, the FF circuit 27 is set, and the reset waiting state is set. Then, at the moment when the inspection light passes the right end of the web 2 in the first scanning, the edge detection bandpass filter 22
Signal C changes to a minus side in a pulse shape, becomes less than or equal to a threshold value (THLD) determined by the reference voltage of the comparator 26, and the comparator 26 outputs a high level end candidate signal D. This end candidate signal D is the FF circuit 2
7 is reset, and the signal level at the output end of the FF circuit 27 is inverted and becomes high level again.

The OS circuit 30 receives the inversion signal F when the FF circuit 27 inverts from the set state to the reset state,
The pulse-shaped end signal G is output. Inspection width setting circuit 31
Becomes high level after measuring the start time T1 from the time of inputting the inverted signal G, and the stop time T2.
The inspection width signal I which becomes low level when the time is measured is output. Then, during the period in which the inspection width signal I is at the high level (T2-T1), the AND circuit 25 is in the gate open state, and the effective inspection period is started.

Immediately before the second scanning of the inspection light is started, the photodetector 3d causes the inspection light detection signal B as described above.
Is input to the timer circuit 28. The timer circuit 28 maintains the FF circuit 27 in the reset state until the fixed time Ts is measured. When the inspection light reflected on the surface of the web 2 is incident on the photodetector 6 by the second scanning, the photoelectric signal A from the photodetector 6 rises, which is the defect detection bandpass filter 21 and the edge detection bandpass. It is input to the filter 22.

The signal C obtained through the bandpass filter 21 along with the scanning of the inspection light is binarized by the binarization circuit 24 and output to the AND circuit 25 as the inspection signal J.
The binarization circuit 24 includes a dark defect pulse P2 in the photoelectric signal A2.
When the bright defect pulse P1 is present, these are all converted into a high level defect signal. Therefore, the inspection signal J becomes a low level signal when the web 2 has no defect and a high level signal when the web 2 has a defect.

At the moment when the photoelectric signal A rises due to the second scanning, the inspection signal J becomes high level, and the binarization circuit 24 outputs this to the AND circuit 25 as a defect signal. Since the inspection width signal I from the setting circuit 31 is still at the low level, the AND circuit 25 does not output a defect signal. In addition, the rising signal of the photoelectric signal A is the bandpass filter 22 for edge detection.
Although it is also input to the comparator 26 after passing through, the output of the comparator 26 is not inverted because it is larger than the threshold value determined by the comparator 26.

When the photoelectric signal A includes a dark defect pulse P2, this is output to the AND circuit 25 as a high-level defect signal by the binarization circuit 24. Further, the band defect filter 22 for edge detection is generated by the dark defect pulse P2.
A negative pulse appears in the signal C from. Since this negative pulse is equal to or less than the threshold value set in the comparator 26, the comparator 26 inputs the plus end candidate signal E to the reset terminal of the FF circuit 27. However, since the timer circuit 28 is still measuring the stop time T2 and the FF circuit 27 maintains the reset state, the end candidate signal E due to the dark defect pulse P2 is ignored.

On the other hand, since the AND circuit 25 is in the gate open state by the inspection width signal I from the inspection width setting circuit 31, the defect signal by the dark defect pulse P2 is output through the AND circuit 25. And AND circuit 2
The generation timing of the defect signal K output from the device 5, the clock pulse indicating the rotation position of the polygon mirror 3a by the scanning mechanism 3 (corresponding to the scanning position of the inspection light), and the extraction timing of the end signal described later are calculated by a computer. The position of the dark defect in the width direction of the web 2 can be specified by making a comparison with.

Immediately before the inspection light passes through the right end of the web 2, the timer circuit 28 finishes measuring the fixed time Ts,
The FF circuit 27 is set by the edge detection permission signal E of the positive pulse. Immediately after that, the inspection width setting circuit 31 completes the measurement of the stop time T2, the inspection width signal I falls to the low level, and the AND circuit 25 is turned off. Therefore, even if a defect signal is generated thereafter, it is not output from the AND circuit 25.

At this point, the inspection light reaches near the right end of the web 2. Assuming that the web 2 meanders to the left side in FIG. 1, as shown in FIG. 2, the inspection light is emitted from the web 2 immediately after the timer circuit 28 finishes measuring the time Ts.
Pass the right edge of. As a result, a negative pulse appears in the signal C as in the case of the dark defect pulse P2, and the FF
The end candidate signal D is input to the circuit 27. FF circuit 27
Is in the set state by the edge detection permission signal E from the timer circuit 28, and therefore F by the edge candidate signal D.
The F circuit 27 is inverted to the reset state, and the inversion signal G from the OS circuit 30 causes the inspection width setting circuit 31 to start counting the start time T1 and the stop time T2 again.

After the inspection width setting circuit 31 measures the start time T1, the AND circuit 25 outputs the high-level inspection width signal I.
Then, the defect detection by the third scanning is started. If the photoelectric signal A contains a bright defect pulse P1, it passes through the AND circuit 25 and becomes the defect signal K. Although the positive pulse is output from the edge detection bandpass filter 22 by the bright defect pulse P1, this pulse is cut by the comparator 26 and does not become the edge candidate signal D.

As described above, in the defect detection circuit 20, the fixed time Ts is measured from the time when the inspection light is detected by the photodetector 3d immediately before the start of each scanning, and the time Ts is obtained after the end of the time measurement. The edge candidate signal D is treated as an effective edge signal, and the inspection width signal I for determining an effective inspection period is generated with reference to the edge signal thus obtained. Therefore, the generation timing of the edge signal changes corresponding to the meandering of the web 2, and the effective inspection period changes accordingly, so that the constant time Ts is set to an appropriate value based on the predicted meandering amount. By setting the values to the values and adjusting the start time T1 and the stop time T2 set in the inspection width setting circuit 31, accurate surface inspection can be performed up to almost the end while following the meandering of the web 2. be able to.

[0037]

EXAMPLE If the number of reflecting surfaces of the polygon mirror 3a is 12 and the number of rotations thereof is 12000 rpm, the number of scanning times is 3000 times per second (one cycle is 333 μsec). Considering the practical arrangement, the scanning angle is 20 ° (the scanning time is about 220 μsec), and the time until the photoelectric signal A rises after scanning the photodetector 3d is 40 μsec.
It will be about.

Here, the inspection width of one of the scanning mechanisms 3, 4, and 5 is 1500 mm, and the meandering is 10 mm.
If it is within the range, the width in which the end portion of the web 2 moves due to meandering is converted into time, 220 μsec × (10/1500) = 1.47 μse
c. Therefore, the maximum value of the constant time Ts is 40 + 220-1.47 = 258.53 (μsec). Based on the above results, when the value of the constant time Ts was set to the range of 240 to 250 μsec and the inspection was actually performed with some allowance, the inspection was successful.

In the example described above, the defect is detected based on the reflected light from the web 2. However, the inspection light transmitted through the web 2 is received by the light receivers 6, 7 and 8 and the transmissive surface. It is also possible to carry out an inspection. Further, although three scanning mechanisms and three photodetectors are arranged side by side in the width direction of the web 2, the number of these may be appropriately increased or decreased according to the width of the web 2. Further, the scanning line of the inspection light by the scanning mechanisms 3, 4, 5 does not necessarily have to be on a straight line, and the set of the scanning mechanism and the light receiver may be arranged so as to be displaced with respect to the traveling direction of the web 2.

[0040]

As described above, according to the surface inspection apparatus of the present invention, in the inspection area including the end portion of the inspection object, the inspection light is scanned from the central portion of the inspection object toward the end portion, Since the effective inspection period in the next inspection area is determined based on the extraction timing of the end signal obtained in the scanning process, even if the inspection object meanders, the inspection area follows the inspection area. Can be determined, and it becomes possible to perform accurate defect detection with almost no dead zone near the edge.

Further, in order to start the end signal extraction operation after the inspection light has finished scanning the defect inspection area, it is determined that the inspection light has passed a certain position immediately before the inspection area is scanned. Is detected, the fixed time required for scanning from the detection time to immediately before the inspection light reaches the end is measured, and the end signal extraction operation is started after the completion of the time measurement. The signal can be discriminated and extracted from the defective signal. Also, based on the extraction timing of the previous edge signal, the effective inspection period is set from the elapse of a certain start time to the elapse of a certain stop time, and the effective inspection period is set regardless of whether there is meandering. Since it is kept constant, it is possible to easily specify the position of the defective portion of the object to be inspected based on the extraction timing of the edge signal or the edge detection timing of the light shielding plate that moves following the meandering. You can

[Brief description of drawings]

FIG. 1 is an explanatory diagram showing a configuration of a surface inspection apparatus embodying the present invention.

FIG. 2 is an explanatory diagram showing an output waveform of each unit of FIG.

[Explanation of symbols]

2 Web 24 Binarization circuit 26 Comparator 27 Flip-flop circuit (FF circuit) 28 timer circuit 31 Inspection width setting circuit

Claims (4)

(57) [Claims] 1. The surface of a continuously running sheet-like object to be inspected is irradiated with inspection light for scanning in the width direction by driving a scanning mechanism, and reflected light or transmitted light is made incident on a light receiver to correspond to the amount of light. In the surface inspection apparatus which obtains the photoelectric signal and evaluates the photoelectric signal to inspect the defect of the inspected object, a plurality of the scanning mechanism and the light receiving device are installed in the width direction of the inspected object, respectively. The scanning mechanism that scans the inspection light in the inspection area including the end portion in the width direction is set so that the scanning direction goes from the central portion of the inspection object to the end portion, and is provided corresponding to the scanning mechanism. An end signal when the inspection light scans the end of the inspected object is extracted from the photoelectric signal output from the light receiver, and the next inspection area by the scanning mechanism is extracted based on the extraction timing of the end signal. To determine the effective inspection period in Surface inspection apparatus according to claim. 2. A photodetector for detecting that the inspection light of the scanning mechanism has passed a predetermined position immediately before scanning the inspection area, and a predetermined time from the time when the photodetector detects the passage of the inspection light. The surface inspection apparatus according to claim 1, wherein the extraction operation of the end signal is started after a lapse of time. 3. The valid inspection period is a constant period from a timing of extracting the end signal to a lapse of a constant start time and a constant stop time. Or the surface inspection device according to 2. 4. The scanning mechanism and the light receiver, each of which is provided in plurality, includes a scanning mechanism and a light receiver having an inspection area that does not include an end portion of an object to be inspected, and a scanning start side of inspection light by the scanning mechanism. Is provided with a light shielding plate for preventing the inspection light from entering the light receiver, and the light shielding plate is moved in the width direction of the object to be inspected while following the meandering of the end portion of the object to be inspected. Detects the reference timing when the inspection light scans the edge of the light shielding plate from the output photoelectric signal, and when the photoelectric signal from the photodetector contains a defect signal, based on the reference timing When the position of the defect in the width direction of the object to be inspected is specified, and the defect signal is included in the photoelectric signal from the light receiver provided corresponding to the inspection area including the end of the object to be inspected, Based on edge signal extraction timing 4. The position of the defect in the width direction of the object to be inspected is specified by the above-mentioned method.
The surface inspection device according to any one of 1.