JPH08278258A - Surface inspection apparatus - Google Patents

Abstract

PURPOSE: To obtain a surface inspection apparatus by which an inspection can be performed surely even when the surface of an object to be inspected is vibrated by a method wherein an incident-light distribution in an inspection position is decided to be a pattern shape comprising two peak points and a reflected-light intensity distribution pattern is flattened. CONSTITUTION: Substantial light radiation parts at an illumination device 2 are formed in two mutually adjacent places, and an identical inspection position PL on a steel plate 1 is illuminated simultaneously. In addition, the direction of the central axis of illumination light which is radiated from two light radiation ports is set properly, a reflected-light-intensity distribution pattern is flattened, and a change in reflected light intensity near a peak position is made gentle. Signals which are output by line sensor cameras 3, 6 are passed through respective signal processing circuits 7, 8 so as to be input respectively to an abnormality judgment circuit 4. Then, the level of a signal which is output by the signal processing circuit 7 is corrected by the level of a signal which is output by the signal processing circuit 8, the level of the signal is compared with a reference level which has been stored in advance, and the abnormality of properties on the surface of the steel plate 1 is discriminated.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a surface inspection apparatus, which can be used for optically inspecting the state of the surface of a steel plate or the like.

[0002]

2. Description of the Related Art In the field of the steel industry, for example, it has been conventionally practiced to optically inspect the surface condition of a steel sheet or the like to inspect for defects on the surface or the surface layer.

As disclosed in, for example, Japanese Patent Application Laid-Open No. 58-204350, a surface inspection apparatus of this type includes an illuminating device for irradiating the surface of the inspection object with light and a light for irradiating the inspection object. A light receiving device installed in the regular reflection direction and an identification device for identifying the surface state of the inspection object according to the light incident on the light receiving device are provided. That is, the intensity of the reflected light entering the light receiving device changes depending on the presence or absence of a flaw.
The presence or absence of a flaw can be identified by the difference in the amount of received light.

Further, in the surface inspection apparatus disclosed in Japanese Patent Laid-Open No. 4-178541, the light receiving device is installed at a position not in the direction of specular reflection, and the illuminating device is constructed so that a curved surface with a predetermined radius of curvature emits light. The focus position of the device is arranged so as to coincide with the inspection position.

[0005]

In this type of surface inspection device, the signal-to-noise ratio of the signal input to the identification device is relatively small. For example, when a region having a flaw is inspected, a light receiving device is used. There is a small difference between the intensity of the incident light and the intensity of the light incident on the light receiving device when inspecting a region where there is no flaw, and it may be difficult to identify the difference.

When the object to be inspected is continuously inspected while being conveyed, it is inevitable that the object to be inspected vibrates. When the inspection object vibrates in the thickness direction (direction perpendicular to the surface), the incident angle of the illumination light slightly changes, and accordingly the specular reflection direction of the reflected light from the inspection object also changes. Since the light-receiving device has a field of view to some extent, it is possible to continuously receive specularly reflected light even when the specularly reflected direction of the reflected light changes. However, when the regular reflection direction of the reflected light changes, the intensity distribution of the reflected light from the inspection object in the visual field of the light receiving device changes. With this, when inspecting an area where a flaw exists, the intensity of light incident on the light receiving device,
When inspecting a region where no flaw exists, the difference with the intensity of light incident on the light receiving device also varies, and it is easy to make an error in determining the presence or absence of a flaw.

Therefore, the present invention provides a surface inspection apparatus,
Even if vibration occurs on the surface to be inspected, it is an object to facilitate correct identification of the surface state.

[0008]

In order to solve the above-mentioned problems, in claim 1, an illuminating device for irradiating the surface of the inspection object (1) with light, and specular reflection of the light irradiated on the inspection object. In a surface inspection device including a light receiving device (3) installed in a direction, and an identification device (4) for identifying the state of the surface of the inspection object according to the light incident on the light receiving device: An illumination mechanism (2, 2B, 2C, 2) for irradiating illumination light from two positions which are adjacent to each other and are spaced apart from each other toward substantially the same inspection position on the surface of the inspection object.
D, 2E) are provided.

Further, in claim 2, the illumination mechanism (2, 2)
C) is two slit-shaped openings (51, 52, 51C, 52C) installed at positions adjacent to each other, and at least one light source (2) that emits light toward these openings.
01, 211, 221) and a diffusion plate (203, 213, 223) installed between the light source and the opening.

Further, in claim 3, the illumination mechanism (2B).
Is a slit-shaped opening (51B, 52B), a light source (211, 221) for irradiating light toward the opening, and an optical lens (23, 2) arranged between the light source and the opening.
4) and two illumination units (21B, 22B) having the above are installed at positions adjacent to each other, and the optical axes of the illumination light of these two illumination units are arranged to be inclined with respect to each other.

Further, in claim 4, the illumination mechanism (2D)
Is a light source (25) that emits beam-like light, and a beam separation mechanism (26, 26) that separates a single light beam emitted from the light source into two light beams. 27) and an optical lens (28) arranged in the path of the two light beams emerging from the beam separating mechanism.

According to a fifth aspect of the invention, the illumination mechanism is a variable diaphragm mechanism (20) installed between the light source and the light exit port.
4, 214, 224).

According to a sixth aspect of the invention, there is provided a movable mechanism (40, 41, 42) for movably supporting at least the position of the diaphragm mechanism of the illuminating device in the optical axis direction of the illumination light.

The symbols shown in the parentheses indicate the reference numerals of the corresponding elements in the embodiments described later for reference. However, each component of the present invention is a specific element in the embodiments. It is not limited to only.

[0015]

For example, as shown in FIG. 1, when light from the light source is incident on the surface of the inspection object at a certain incident angle θ1, there is a certain spread around the reflection angle θ2 (that is, the regular reflection direction) equal to θ1. Reflected light goes to the area that it has. That is,
The reflected light intensity distribution is expressed by the following equation.

[0016]

## EQU1 ## Reflected light intensity distribution = incident light intensity distribution * reflection distribution characteristic *: convolution For example, when the inspection object is a steel sheet, the reflection distribution characteristic is mainly determined according to the surface roughness of the steel sheet. If the surface property of the steel sheet is abnormal, the reflection distribution characteristic also changes, so that the reflected light intensity distribution changes between the normal portion and the abnormal portion of the inspection object as shown in FIG.

On the other hand, the viewing angle θ of the light receiver on which the reflected light is incident
Since v has a certain magnitude, when the light receiver is arranged in the regular reflection direction as shown in FIG. 1, the total energy of the reflected light in the range included in the viewing angle θv in the reflected light intensity distribution is −. The light amount corresponding to is detected by the light receiver.

For example, when θv1 shown in FIG. 2 is the visual field of the light receiver, the total energy contained in the visual field θv1 is obviously different between the reflected light in the abnormal portion and the reflected light in the normal portion. By determining the detection level of the light receiver, it is possible to identify whether the surface to be inspected is a normal part or an abnormal part. However, for example, when θv2 shown in FIG. 2 is the field of view of the light receiver, the “abnormal part” appears near the center of the field of view.
>"Normalpart", and conversely "abnormal part" in the peripheral part of the visual field
<Because it is a “normal part”, the total energy contained in the visual field θv2 does not have a large difference between the reflected light of the abnormal part and the reflected light of the normal part, and due to the slight difference in the size of the visual field, The magnitude relationship may be reversed. Therefore, when the field of view is θv2, the S / N of the signal obtained by the photodetector is
The ratio is so low that reliable testing is not possible.

Even if θv1 shown in FIG. 2 matches the viewing angle of the light receiver, if the center of the viewing field does not match the direction of the peak of the reflected light intensity, the viewing field is θv2. As with some cases, reliable testing is not possible. In fact, for example, when inspecting the surface of a steel sheet while it is being transported, the steel sheet vibrates in its thickness direction, so the incident angle of the illumination light on the steel sheet slightly changes, and the reflected light from the steel sheet is directed. Since the direction also fluctuates, the reflected light intensity distribution in the visual field of the light receiver fluctuates. Therefore, the S / N ratio of the signal obtained by the light receiver is very low, and highly reliable inspection cannot be performed. In particular, the change in the reflected light intensity with respect to the difference in the reflection angle is large. For example, when the curve of the reflected intensity distribution pattern is steep as shown in FIG. 2, the allowable range of the inspection device for the vibration of the steel sheet is small. Become.

On the other hand, in the apparatus according to the first aspect, the illumination mechanism for irradiating the illumination light from the two positions which are adjacent to each other with a space therebetween, toward the substantially same inspection position on the surface of the inspection object ( 2, 2B, 2C, 2D, 2E). That is, when viewed from the inspection position on the surface of the inspection object, the light sources are present at two locations that are close to each other, so the intensity distribution of the incident light (illumination light) in the incident angle direction at the inspection position is
For example, the characteristic CB shown in FIG. 9 is obtained. Further, as shown in FIG. 9, the reflected light intensity distribution changes according to the difference in the incident light intensity distribution, and when the incident light intensity distribution has the characteristic CA (when there is one light source position), the reflected light intensity distribution Has a characteristic CC, and when the incident light intensity distribution has a characteristic CB, the reflected light intensity distribution has a characteristic CD.

For example, in the reflected light intensity distribution of FIG.
In the range of “normal part <abnormal part”, the characteristic CC is θx1,
Characteristic CD is θx2, clearly “θx1 <θx2”
Is. As described above, when the angle of the reflected light changes due to the vibration of the inspection object or the like, the peak direction of the reflected light intensity deviates from the direction of the central axis of the field of view of the light receiver. For example, in FIG.
In the example of the characteristic CC in the case where the field of view of the light receiver is θx1, if the direction of the reflected light is slightly deviated from the direction of the central axis of the field of view of the light receiver, the range of the field of view includes the region of “normal part> abnormal part”. Therefore, it is difficult to distinguish between normal and abnormal. On the other hand, in the example of the characteristic CD in FIG. 9, the field of view of the light receiver is θx.
In the case of 1, even if the direction of the reflected light deviates by (θx2-θx1) / 2 from the direction of the central axis of the field of view of the light receiver, “normal part <abnormal part” is satisfied over the entire area of the field of view.
It is easy to identify abnormalities. That is, according to the present invention, by arranging the substantial light source positions at two positions close to each other, it is possible to mitigate the adverse effect on the inspection due to the vibration of the inspection object.

By setting the light source positions at two positions close to each other and providing a space between the two light source positions,
A reflected light intensity distribution like the characteristic CD in FIG. 9 can be obtained. However, as shown in, for example, Japanese Patent Application Laid-Open No. 4-178541, the characteristic C can be obtained by simply irradiating illumination light from a wide range.
A reflected light intensity distribution like D cannot be obtained.

In the second aspect, two slit-shaped openings (51, 52, 5) installed at positions adjacent to each other.
1C, 52C) and at least one light source (201, 211, 221) for irradiating light toward these openings,
A diffuser plate (203, installed between the light source and the opening)
213, 223) are provided in the illumination mechanism (2, 2C). By providing the two slit-shaped openings, the light source positions can be provided at two locations close to each other. Further, by disposing a diffuser plate between the light source and the opening, the incident light intensity distribution of the illumination light incident on the inspection surface can be obtained without adjusting the directions of the respective optical axes of the illuminating device precisely.
As shown in 0, the pattern of the reflected light intensity distribution can be stabilized, and the range where the normal / abnormal of the reflected light intensity distribution can be easily distinguished can be widened.

In the third aspect, the slit-shaped openings (51B, 52B), the light sources (211, 221) for irradiating light toward the openings, and the optics arranged between the light sources and the openings. Two illumination units (21B, 22B) having lenses (23, 24) are installed at positions adjacent to each other, and the optical axes of the illumination light of the two illumination units are arranged to be inclined with respect to each other. In each illumination unit, the light emitted from the light source is condensed by the optical lenses (23, 24), passes through the openings (51B, 52B), and is focused at a predetermined position. By adjusting the inclinations of the optical axes of the two illumination units, the illumination light emitted from two locations can be adjusted to one on the inspection object.
It can be set to focus at one inspection position. As a result, the incident light intensity distribution at the inspection position is shown in FIG.
It can be made uniform as indicated by 0.

According to a fourth aspect of the present invention, a single light beam emitted from one light source (25) is a beam separating mechanism (2).
6, 27) and separated into two light beams, and each light beam is focused by an optical lens (28) and focused at one inspection position on the inspection object. To be done. This makes it possible to flatten the incident light intensity distribution at the inspection position as shown in FIG.

Further, in the present invention, the variable diaphragm mechanism (204, 214, 224) is installed between the light source and the light emitting port. By adjusting the aperture amount (for example, aperture width), the spread width of the incident light intensity distribution (θw1, θ in FIG. 10)
w2, θw3) can be changed. When the spread width of the incident light intensity distribution is changed, the pattern of the reflected light intensity distribution changes accordingly. Therefore, the pattern of the reflected light intensity distribution should be the most preferable (the range (θx1 to θx5) in which the difference according to the presence / absence of abnormality in the reflected light intensity distribution occurs)
Is wide and the difference is large) can be adjusted.

In the sixth aspect, the movable mechanism (40, 4
1, 42), the position of the diaphragm mechanism can be moved in the optical axis direction of the illumination light. When the position of the diaphragm mechanism is moved in the optical axis direction of the illumination light, the spread width (θw1, θw2, θw3 in FIG. 10) of the incident light intensity distribution is changed even if the diaphragm amount (for example, the aperture width) is constant. be able to. Therefore, the pattern of the reflected light intensity distribution should be most preferable (so that the range (θx1 to θx5) in which the difference depending on the presence / absence of abnormality in the reflected light intensity distribution is wide and the difference becomes large) It is possible to adjust.

In the example of FIG. 3, the incident angle spread θL (see FIG.
(Corresponding to θw1 to θw3 of 0) is 4 degrees of 5 degrees, 10 degrees, 15 degrees, and 30 degrees, respectively, and incident light intensity distribution and reflected light intensity distribution (normal portion and abnormal portion, respectively)
Is shown. Referring to FIG. 3, the incident angle spread θL
It can be seen that the pattern of the reflected light intensity distribution changes in accordance with. Further, assuming a certain range as the viewing angle θv of the light receiver, as shown in FIG. 3, the total energy within the viewing angle θv, that is, the amount of light received by the light receiver is the spread of the incident angle θL.
It turns out that it changes according to.

In the example of FIG. 3, when the incident angle spread θL is 5 degrees or 10 degrees, an area of "abnormal part">"normalpart" and "abnormal part"<"normalpart" in the visual field. Since the area is included, the total amount of energy included in the visual field θv does not significantly differ between the reflected light of the abnormal portion and the reflected light of the normal portion due to the cancellation of the two areas. Also, the spread of the incident angle θL
Is 30 degrees, the "abnormal part" = "normal part" in the entire visual field. Therefore, the total energy contained in the visual field θv is the reflected light of the abnormal part and the reflection of the normal part. There is no big difference with light. On the other hand, when the incident angle spread θL is 15 degrees, the total sum of the energy contained in the visual field θv is also “abnormal part”> because the “abnormal part”> “normal part” in the entire visual field. It becomes a "normal part", and the presence or absence of abnormality can be easily identified based on the amount of light received by the light receiver.

Therefore, if the object to be inspected does not vibrate, the variable diaphragm of the illumination device is operated to adjust the spread θL of the incident angle of the illumination light so that the abnormality can be easily identified (for example, as shown in FIG. 3 (θL = 15 degrees). The adjustment of such illumination significantly improves the reliability of the inspection.

[0031]

EXAMPLE FIG. 4 shows the configuration of the entire surface inspection apparatus of one example. Referring to FIG. 4, this surface inspection apparatus includes an illumination device 2, a line sensor camera 3, 6, a signal processing circuit 7,
8 and an abnormality determination circuit 4. The steel sheet 1 as the inspection object is inspected while being conveyed at a constant speed in the longitudinal direction indicated by Y in the drawing.

The illumination device 2 is suspended and fixed from above by a support mechanism (not shown). Lighting device 2
Illuminates the illumination light from the light exit port 5 toward the surface of the steel plate 1. However, as will be described later, the substantial light exit ports of the illuminating device 2 are provided at two locations close to each other. And
The light emitted from the two light emission ports is configured to simultaneously illuminate the same inspection position PL on the steel plate 1. Further, the directions of the central axes of the illumination light emitted from the two light emission ports are arranged so as to be inclined with respect to the surface of the steel sheet 1 at the angles PL and θ1a and θ1b, respectively.
The light emitted from the lighting device 2 simultaneously illuminates the entire width direction (X direction) of the steel plate 1. That is, at the position PL where the central axis of each illumination light emitted from the lighting device 2 and the surface of the steel plate 1 intersect, the angle formed by the central axis of the illumination light and the surface of the steel plate 1, that is, the incident angle of light is θ1a and θ1a, respectively. becomes θ1b.

However, as will be described later, since the illumination is performed through the slit, the incident angle of the illumination light at the position PL is
As shown in FIG. 3, it has a width θL. Width θL
The size of is determined according to the slit width.

On the other hand, the line sensor camera 3 is positioned and fixed so that the central axis of its field of view faces the position PL on the steel plate 1. Further, the position PL on the steel plate 1
The angle θ2 between the surface of the steel plate 1 and the central axis of the field of view of the line sensor camera 3 coincides with the incident angle θ1 of the illumination light incident on the steel plate 1 from the lighting device 2 (the angle between the angles θ1a and θ1b). Is positioned as. That is, the line sensor camera 3 is arranged toward the regular reflection direction of the illumination light emitted from the illumination device 2 and reflected on the surface of the steel plate 1.

As shown in FIG. 1, when the light from the light source is incident on the surface of the object to be inspected at a certain incident angle θ1, there is a certain spread around the reflection angle θ2 (that is, the regular reflection direction) equal to θ1. The reflected light goes to the area where That is, the reflected light intensity distribution is expressed by the following equation.

[0036]

## EQU00002 ## Reflected light intensity distribution = incident light intensity distribution * surface reflection distribution characteristic *: convolution When the inspection object is a steel sheet, the reflection distribution characteristic is mainly determined according to the surface roughness of the steel sheet. If the surface property of the steel sheet is abnormal, the reflection distribution characteristic also changes, so that the reflected light intensity distribution changes between the normal portion and the abnormal portion of the inspection object as shown in FIG. This difference in reflected light intensity distribution
Whether or not there is an abnormality in the surface properties of the steel plate by distinguishing from the signal detected by the line sensor camera 3 (presence or absence of a flaw, etc.)
Is determined. The line sensor camera 3 is 1 in the X-axis direction.
A large number (for example, 4096) of light receiving elements arranged in a row are built in, and the respective light receiving elements simultaneously receive the reflected light from each position of the full width at the position PL on the steel plate 1. Therefore, the entire inspection in the width direction can be performed once without performing mechanical scanning. When the width of the inspection object is wide, the entire width can be inspected by arranging a large number of sets of light sources and detectors in the width direction.

On the other hand, another line sensor camera 6
Is positioned and fixed such that the central axis of the visual field is directed to the position PL on the steel plate 1, but the central axis of the visual field is perpendicular to the surface of the steel plate 1 at the position P.
It is installed above L. Therefore, the line sensor camera 6 detects the component of the light diffusely reflected on the surface of the steel plate 1. The line sensor camera 6 also has a large number (for example, 4096) of light receiving elements arranged in a line in the X-axis direction, and simultaneously receives the reflected light from each position of the full width at the position PL on the steel plate 1, respectively. Receives light.

Even if the line sensor camera 6 for detecting diffused reflection light is omitted, it is possible to determine whether or not there is an abnormality in the surface property of the steel plate. In this embodiment, even if the type of the steel plate 1 is changed or the installation state of the lighting device 2 or the line sensor camera 3 is changed, it is possible to determine the abnormality of the steel plate surface property without adjustment so as to be an auxiliary. The line sensor camera 6 is installed in the.

The signal output from the line sensor camera 3 passes through the signal processing circuit 7, the signal output from the line sensor camera 6 passes through the signal processing circuit 8, and the abnormality determination circuit 4 respectively.
Is input to The abnormality determination circuit 4 determines the level of the signal output by the signal processing circuit 7 (the light amount level of the specular reflection light from each position detected by the line sensor camera 3).
Is corrected by the level of the signal output by the line sensor (the light amount level of the diffused reflected light from each position detected by the line sensor camera 6), and then the signal level is compared with a prestored reference level to determine a difference between the two. When it is above, it is determined that the surface property of the steel sheet 1 is abnormal, and when it is other than that, it is determined that it is normal. The reference level is a signal level obtained by inspecting the surface of the steel sheet whose surface property is confirmed to be more normal by visual inspection or the like with the line sensor cameras 3 and 6, and the reference level is a special update instruction. It is held in the abnormality determination circuit 4 until there is.

FIG. 5 is a vertical sectional view of the illuminating device 2 shown in FIG.
Shown in Referring to FIG. 5, the lighting device 2 is configured by vertically stacking two lighting mechanisms 21 and 22 having the same structure. Each of the illumination mechanisms 21 and 22 has a straight tube-shaped fluorescent lamp 211, 2 extending in the X-axis direction.
21, parabolic mirrors 212 and 222, and a translucent diffusion plate 2
13 and 223, and variable diaphragm mechanisms 214 and 224 arranged near the light exit port.

The light emitted from the fluorescent lamp 211 is reflected by the parabolic mirror 212 and becomes a substantially parallel light beam in the direction of arrow A. Further, this light flux passes through the diffusion plate 213 and is diffused in the direction of arrow B, and a part thereof passes through the slit-shaped opening 51 formed by the variable diaphragm mechanism 214 and arrow A
Direction and a direction slightly inclined with respect to the axis thereof, that is, in the direction toward the surface of the steel plate 1. Similarly, the light emitted from the fluorescent lamp 221 is reflected by the parabolic mirror 222 and becomes a substantially parallel luminous flux in the arrow A direction. Furthermore,
This light flux passes through the diffusion plate 223 and diffuses in the direction of arrow B, and a part thereof passes through the slit-shaped opening 52 formed by the variable diaphragm mechanism 224 in the direction of arrow A and a direction slightly inclined with respect to its axis. Is emitted.

The variable diaphragm mechanism 214 has rectangular (thin plate) light-shielding plates 215 and 217 made of a flexible material.
Is equipped with up and down. The light shielding plate 215 is sandwiched by the casing inner wall of the illumination mechanism 21 and the roller 216, and is deformed according to the shape of the casing inner wall. Roller 216
Is rotatably supported and is connected to a drive shaft of an electric motor (not shown). When this electric motor is driven, the roller 216 rotates, and the light shielding plate 215 moves accordingly. Similarly, the light shielding plate 217 is sandwiched between the casing inner wall of the illumination mechanism 21 and the roller 218,
It is deformed according to the shape of the inner wall of the casing. Roller 2
18 is rotatably supported, and the electric motor 18 is
Is connected to the drive shaft of the motor. When the electric motor is driven, the roller 218 rotates, and along with that, the light shielding plate 21.
7 moves.

Similarly, the variable diaphragm mechanism 224 is provided with rectangular (thin plate-shaped) light shielding plates 225 and 227 made of a flexible material in the upper and lower directions. The light shielding plate 225 is sandwiched by the casing inner wall of the illumination mechanism 22 and the roller 226, and is deformed according to the shape of the casing inner wall. B
The rotor 226 is rotatably supported and is connected to the drive shaft of the electric motor. When the electric motor is driven, the roller 226 rotates, and along with that, the light shielding plate 2
25 moves. Similarly, the light blocking plate 227 is used for the illumination mechanism 2
It is sandwiched between the inner casing wall 2 and the roller 228 and is deformed according to the shape of the inner casing wall. Roller 22
8 is rotatably supported and is also connected to the drive shaft of the electric motor. When you drive an electric motor,
The roller 228 rotates, and the light blocking plate 227 moves accordingly.

In this embodiment, when the electric motor is driven in the normal direction, the light shielding plates 215 and 225 rise, and the light shielding plate 21 is moved.
7,227 descends. Further, when the electric motor is driven in the reverse direction, the light shielding plates 215 and 225 descend and the light shielding plates 217, 217,
227 rises. Therefore, when the electric motor is driven in the normal direction, the slit width Wsb of the opening 51 between the light shielding plates 215 and 217 and the slit width Wsa of the opening 52 between the light shielding plates 225 and 227 are increased, and the reverse rotation driving is performed. Then, the slit widths Wsb and Wsa are reduced. The forward rotation drive, reverse rotation drive, and stop control of the electric motor are executed in response to the operation of a switch (not shown). Further, the slit widths Wsb and Wsa are always controlled to be substantially the same.

The openings 51 and 52 are elongated (slit-like) in the X direction and have a length substantially equal to the entire width of the steel plate 1. Therefore, it is possible to simultaneously illuminate the range over the entire width of the steel plate 1.

The light emitted from the light emitting port 5 of the illuminating device 2 is limited according to the size of the openings of the variable diaphragm mechanisms 214 and 224, that is, the slit widths Wsa and Wsb, as shown in FIG. For example, as shown in FIG. 6, the spread width θw3 of the incident angle of the illumination light that enters the inspection position PL on the steel plate 1 through the opening 51 is determined according to the slit width Wsb, and the opening 5 is formed.
The spread width θw3 of the incident angle of the illumination light that enters the inspection position PL on the steel plate 1 through 2 is determined according to the slit width Wsa. That is, the spread width θw3 of the illumination light can be changed by changing the slit widths Wsa and Wsb. Further, since the illumination light is diffused by the diffusion plates 213 and 223 and then passes through the openings 51 and 52, the intensity distribution of the illumination light within the range of θw3 becomes substantially uniform. Therefore, the steel plate 1
The intensity distribution with respect to the incident angle of the illumination light at the upper position PL has a characteristic D3 shown in FIG.

As can be seen from the above equation 2, even if the reflection distribution characteristic of the steel sheet 1 to be inspected is constant, if the incident light intensity distribution changes, the reflected light intensity distribution also changes. Actually, it becomes as shown in FIG. FIG. 3 is a spread width θL of incident light, that is, illumination light (corresponding to θw1, θw2, and θw3 in FIG. 10).
Shows the incident light intensity distribution and the reflected light intensity distribution in the respective cases of 5 degrees, 10 degrees, 15 degrees and 30 degrees. The distribution of reflected light intensity shows both the case where the surface properties of the steel sheet 1 are normal and the case where the surface properties are abnormal. Further, θv shown in FIG. 3 is a light receiver (line sensor camera 3
Is equivalent to the viewing angle.

Referring to FIG. 3, the spread width θL of the illumination light
It can be seen that the pattern of the reflected light intensity distribution is different depending on whether the surface texture of the steel sheet 1 is normal or abnormal regardless of whether the surface is 5 degrees, 10 degrees, 15 degrees or 30 degrees. However, since the light quantity of the reflected light actually detected by the light receiver is an average light quantity level within the range of the viewing angle θv, it is difficult to identify the difference even if the patterns are different. There are cases. For example, in the example of θL = 5 degrees in FIG. 3, “reflected light intensity of normal part” <near the center of the visual field.
"Reflected light intensity of abnormal area" is, but "reflective light intensity of normal area">"reflected light intensity of abnormal area" in the peripheral area of the field of view, so the amount of light received near the center of the visual field and the peripheral area By canceling out with the received light amount of, there is almost no difference in the light amount level detected by the light receiver between the normal portion and the abnormal portion. Also,
In the example of θL = 30 degrees in FIG. 3, the “reflected light intensity of the normal portion” and the “reflected light intensity of the abnormal portion” are over the entire visual field.
Since there is almost no difference between the normal part and the abnormal part, there is almost no difference in the light amount level detected by the light receiver.

On the other hand, in the example of θL = 15 degrees in FIG. 3, since "reflected light intensity of normal part"<"reflected light intensity of abnormal part" over the entire field of view, the amount of light detected by the light receiver is The level clearly differs between the normal part and the abnormal part. That is, if the relationship between the reflected light intensity distribution pattern and the viewing angle θv is set as in the case of θL = 15 degrees in FIG. 3, the reliability of the surface inspection can be improved. Viewing angle θ
Assuming that v is fixed, it can be set as in the case of θL = 15 degrees in FIG. 3 by adjusting the incident light intensity distribution of the illumination light.

Since the illuminating device shown in FIG. 5 is used in this embodiment, the incident light intensity distribution at the inspection position PL on the steel plate 1 has a characteristic D3 shown in FIG. That is, a range having a spread width of θw3 centered on the incident angle θ1a and a range having a spread width of θw3 centered on the incident angle θ1b have uniform incident light intensity, and the other range (of θ1a and θ1b). The incident light intensity becomes zero in a range including a spread width of θw3 around the intermediate incident angle θ1).

FIG. 10 shows an incident light intensity distribution and a corresponding reflected light intensity distribution. Three types of incident light intensity distributions, D1, D2, and D3, are shown, and reflected light intensity distributions E1, E2, and E3 of two types of inspected objects having normal surface properties and abnormal surface properties are shown. It is shown. In the incident light intensity distribution of the characteristic D1,
The incident light intensity is uniform in a range having a spread width of θw1 around the incident angle θ1, and the incident light intensity is zero in other ranges. Further, in the incident light intensity distribution of the characteristic D2, the incident light intensity is uniform in a range having a spread width of θw2 around the incident angle θ1, and the incident light intensity is zero in other ranges. Then, “θw1 = θw3 =
θw2 / 2 ”.

Reflected light intensity distributions E1, E2 and E in FIG.
3, the magnitudes θx3, θx4, and θx5 of the range where the reflected light intensity is “abnormal”> “normal” are different from each other. That is, “θx3 <θx4 <θx5”.
Assuming that the viewing angle θv of the light receiver is the same as θx4, the reflected light intensity distribution of the characteristic E1 is within the range where the reflected light intensity is “abnormal”> “normal” within the light field of the light receiver. Since both "abnormal" and "normal" are included, it is difficult to distinguish normal / abnormal by the difference in the level detected by the light receiver. Regarding the reflected light intensity distribution of the characteristic E2,
The reflected light intensity is “abnormal”> “normal”. However, if the center of the field of view of the light receiver is deviated from the peak position of the reflected light intensity distribution, the characteristic E2 has the same result as the characteristic E1.

On the other hand, regarding the reflected light intensity distribution of the characteristic E3, the reflected light intensity is "abnormal">"normal" in the entire area within the visual field of the light receiver. Moreover, since “θx5> viewing angle”, even if the center of the field of view of the light receiver is slightly displaced from the peak position of the reflected light intensity distribution due to the vibration of the steel plate 1, for example, within the field of view of the light receiver. The reflected light intensity is maintained as “abnormal”> “normal” over the entire area. Therefore, it is possible to reliably identify normality / abnormality based on the difference in level detected by the light receiver.

By the way, for example, if the spread width θw2 in the incident light intensity distribution of the characteristic D2 is further increased, the size θx4 in the range of “abnormal”> “normal” in the reflected light intensity distribution E2 is increased and θx4 is changed. It can be larger than the angle of view. Therefore, with respect to the shift between the center of the visual field of the light receiver and the position of the reflected light intensity distribution peak caused by the vibration of the steel plate, the spread width θw in the incident light intensity distribution
Even if 2 is simply increased, some effect can be obtained.

However, in general, in a light receiver, the light receiving sensitivity tends to be higher as it is closer to the center of the visual field. When the reflected light intensity distribution pattern is relatively sharp, the received light intensity distribution within the field of view of the light receiver changes greatly depending on the degree of positional deviation between the peak position of the reflected light distribution and the center of the field of view. For,
The light reception level detected by the light receiver is also affected by the positional deviation. When the peak position of the reflected light intensity distribution and the center of the field of view of the light receiver are displaced, the difference in the light receiving level between "abnormal" and "normal" becomes small, and it is difficult to distinguish between normal and abnormal. become. Therefore, with respect to the shift between the center of the field of view of the light receiver and the peak position of the reflected light intensity distribution caused by the vibration of the steel plate, the reflected light intensity distribution pattern is flattened, especially in the vicinity of the peak position. It is desirable that the change in reflected light intensity be gentle.

For example, only by increasing the spread width θw2 in the incident light intensity distribution of the characteristic D2, there is almost no change in the pattern shape of the reflected light intensity distribution, and the received light intensity distribution in the visual field of the light receiver does not become flat. . However, if the incident light intensity distribution is defined as the characteristic D3 and the incident light intensity in the vicinity of the illumination optical axis position (incident angle: θ1) is made smaller than that in the surroundings, the reflected light intensity distribution becomes the characteristic E3. Therefore, the received light intensity distribution in the visual field of the light receiver is flat. That is, when the incident light intensity distribution like the characteristic D3 is obtained,
Even when the center of the field of view of the light receiver and the peak position of the reflected light intensity distribution are deviated due to the vibration of the steel plate, it is easy to distinguish the abnormality / normality of the surface property of the steel plate.

In this embodiment, as shown in FIG. 6, of the light emitted from the light emission port 5 of the illuminating device, the width of the light incident on the inspection position PL on the steel plate 1 through the opening 51 in the incident direction. θw3 is determined according to the slit width Wsb, and the opening 5
The spread width θw3 in the incident direction of the light that enters the inspection position PL on the steel plate 1 through the line 2 is determined according to the slit width Wsa. Further, there is no illumination light that enters the inspection position PL on the steel plate 1 from the portions other than the openings 51 and 52. Therefore, the incident light intensity distribution of the illumination at the inspection position PL on the steel plate 1 is as shown by the characteristic D3 in FIG. Spread width in incident direction θ
w3 can be changed as necessary by adjusting the slit widths Wsa and Wsb.

The slit widths Wsa and Wsb are adjusted by the following work, for example. Prepare a first steel sheet whose surface texture is confirmed to be normal in advance, and a second steel sheet whose surface texture is previously confirmed to be abnormal (the same type as the first steel sheet), The level of the signal obtained at the output of the signal processing circuit 7 when the first steel plate is inspected (or that corrected by the output of the signal processing circuit 8),
With reference to the level of the signal obtained at the output of the signal processing circuit 7 when inspecting the second steel plate (or that corrected by the output of the signal processing circuit 8), the difference between the two should be as large as possible. The slit widths Wsa and Wsb are adjusted. Further, the first steel sheet and the second steel sheet are respectively subjected to surface inspection in an actual inspection environment, that is, while conveying the steel sheet using actual equipment, so that the difference in signal level between the two is as large as possible. Slit width Wsa, Ws
Readjust b.

A modified example of the illumination device is shown in FIG. Note that, in FIG. 7, the same components as those in the above-described embodiment are designated by the same reference numerals. This will be described with reference to FIG. In this embodiment, lenses 23 and 24 are provided instead of the diffusion plates 213 and 223 of FIG. Therefore, the light emitted from the fluorescent lamp 211 is reflected by the parabolic mirror 212 and becomes a light beam directed in the arrow A direction. Further, this light flux is condensed through the lens 23 so as to be focused at the inspection position PL on the steel plate 1, and only a part of the light passing through the opening 51B of the variable diaphragm mechanism 214 is inspected on the steel plate 1 as illumination light. Position P
It is incident on L. Similarly, the light emitted from the fluorescent lamp 221 is reflected by the parabolic mirror 222 to be a light beam traveling in the direction of the arrow A, passes through the lens 24, and is focused so as to be focused at the inspection position PL on the steel plate 1. , The aperture 52 of the variable diaphragm mechanism 224
Only a part of the light passing through B enters the inspection position PL on the steel plate 1 as illumination light.

In the embodiment shown in FIG. 7, two illumination mechanisms 21 are provided.
The front sides of B and 22B are engaged with each other by the engaging portion 61, and the rear sides of the B and 22B are held by a movable spacer 62 which is inserted between them. By changing the position of the spacer 62 or changing the thickness of the spacer 62, the illumination mechanism 2
The relative tilt angle between the casing of 1B and the casing of the illumination mechanism 22B can be adjusted. Lighting mechanism 21
Since the optical axis of the illumination light emitted from each of B and 22B is determined by the direction of each casing, the adjustment of the spacer 62 allows the optical axis of each of the two illumination mechanisms 21B and 22B to be the focal point. The optical axis can be aligned so as to go to the inspection position PL above 1.

Another modification of the lighting device is shown in FIG. This will be described with reference to FIG. In this example,
The light emitted from the single light source is configured to be emitted from the two light emission ports, and the single illumination mechanism 20 configures the illumination device 2C. The light emitted from the fluorescent lamp 201 is reflected by the parabolic mirror 202 and becomes a light beam traveling in the direction of arrow A,
Only a part of the light that has been diffused through the diffusion plate 203 and has passed through the openings 51C and 52C of the variable diaphragm mechanism 204 enters the inspection position PL on the steel plate 1 as illumination light. The variable diaphragm mechanism 204 includes three light shielding plates 205, 206 and 207.
It has.

The shading plate 205 has a shaft 2 whose one end is rotatable.
The shading plate 206 is supported by a rotatable shaft 209 at its center portion, and the shading plate 207 is supported by a rotatable shaft 210 at one end thereof.
The shafts 208, 209 and 210 are connected to the drive shaft of one electric motor (not shown). By driving this electric motor, the shafts 208, 209 and 210 rotate in the clockwise direction or the counterclockwise direction. When the shafts 208, 209 and 210 rotate clockwise from the state shown in FIG. 8, the slit width Ws of the openings 51C and 52C increases, and when they rotate counterclockwise, the slit width Ws decreases.

Another embodiment of the surface inspection apparatus is shown in FIG.
Shown in Note that, in FIG. 11, the same as the embodiment shown in FIG. 4 except the illumination device 2D and the detector. This will be described with reference to FIG. In this embodiment, the lighting device 2D is a
The light source 25, Hahmira-26, reflecting mirror 27, lens 2
8 and a scanning mechanism 29. The scanning mechanism 29 is
Polygon mirror-2 that rotates at high speed in synchronization with the speed of the steel plate-1
91 and a reflecting mirror 292 that reflects the light emitted from the polygon mirror-291 and guides it to the surface of the steel plate 1. The reflecting mirror 292 has a curved shape with a size larger than the width of the steel plate 1 and keeps the steel plate while keeping the reflected light of the polygon mirror-291 and the Y-axis direction (longitudinal direction of the steel plate) at a constant angle. -Then can be irradiated. The reflected light at this time is a pipe receiver 3 composed of a light guide rod and a photomultiplier tube.
B, 6B is used for detection. This pipe receiver 3B
By using, regardless of the steel plate width direction position,
Only the component of the regular reflection light of the illumination light having a constant angle can be received.

Half of the laser light emitted from the laser light source 101 passes through the half mirror 26, passes through the lens 28 through the first optical path, and the polygon mirror 291 and the reflecting mirror 292. It is reflected by and is incident on the surface of the steel plate 1. The other half of the laser light emitted from the laser light source 101 is reflected by the half mirror 26, then reflected by the reflecting mirror 27, and passes through the lens 28 through the second optical path. , Is reflected by the polygon mirror-291 and the reflecting mirror 292, and enters the surface of the steel plate 1. The incident angle of the illumination light passing through the first optical path to the steel plate surface is θ1b, and the incident angle of the illumination light passing through the second optical path to the steel plate surface is θ1a, θ1a
<Θ1b. Therefore, the incident light intensity distribution of the illumination light incident on the surface of the steel plate is as shown in, for example, the characteristic CB of FIG. 9, so that the reflected light intensity distribution pattern is flattened as in the case of the above embodiment. .

The lens 28 is adjusted in advance so that the laser light emitted from the laser light source 101 is focused on the surface of the inspection position of the steel plate 1.

In the structure of the embodiment shown in FIG. 11, the incident light intensity distribution pattern of the illumination light is constant, but the structure may be changed so that the incident light intensity distribution pattern can be adjusted. For example, using a beam expander, a laser beam
If the beam diameter is enlarged, the beam diameter can be changed by the diaphragm adjusting mechanism. Therefore, a beam expander is installed between the lens 28 and the harf mirror 26 and the reflecting mirror 27, and the beam expander and the lens are expanded. If a variable diaphragm mechanism such as an iris diaphragm is installed between the lens 28 and 28, the incident light intensity distribution pattern becomes variable. A cylindrical lens may be used instead of the beam expander.

Another embodiment of the surface inspection apparatus is shown in FIG.
Shown in Note that, in FIG. 12, except for the illumination device 2E, FIG.
The same as the embodiment shown in FIG. This will be described with reference to FIG. The guide member 40 formed of a thin plate-like metal fitting is fixedly supported in a state of being inclined at a predetermined angle (θ1).
The illuminating device 2E is engaged with the long holes 40a and 40b formed in the guide member 40 at both ends in the width direction, respectively, and extends along the long holes 40a and 40b in the direction of arrow D (the optical axis of the illumination light. It is movable in parallel). Also, the fixture 4
By squeezing 1, 42, the position of the lighting device 2E can be fixed. The configuration of the lighting device 2E is shown in FIG.
The illumination device 2 is the same as the illumination device 2 except that the variable aperture mechanisms 214 and 224 of the illumination device 2 are changed to fixed aperture mechanisms.

In this embodiment, the slit width Ws of the illuminating device 2E is constant, but the distance L between the slit and the illuminating position PL on the steel plate is adjusted by adjusting the position of the illuminating device 2E in the direction of arrow D. Change. Even if the slit width Ws is constant, if the distance L changes, the distribution range θL of the illumination light at the illumination position PL changes, so that the distribution range θL of the illumination light with respect to the incident angle is adjusted as in the above embodiment. can do.

When inspecting a spot-like area, a point light source may be used as the light source, or the scanning mechanism 29 in the embodiment of FIG. 11 may be omitted. A general light receiving device may be used instead of the line sensor cameras 3 and 6. Further, the material to be inspected is not limited to the steel plate, and the material of the present invention may be inspected as long as the reflection characteristic changes according to the surface texture.

[Brief description of drawings]

FIG. 1 is a schematic diagram showing a configuration of a general surface inspection apparatus.

FIG. 2 is a graph showing a reflected light intensity distribution obtained from a steel plate having a normal surface texture and a steel plate having an abnormal surface texture.

FIG. 3 is a graph showing four types of incident light intensity distributions and a reflected light intensity distribution for each incident light.

FIG. 4 is a perspective view showing the configuration of the entire surface inspection apparatus of one embodiment.

5 is a vertical cross-sectional view of the lighting device 2 shown in FIG.

FIG. 6 is a schematic diagram showing a main part of an optical path of light emitted from the illumination device 2.

FIG. 7 is a vertical sectional view showing a modified example of the lighting device.

FIG. 8 is a vertical cross-sectional view showing another modification of the lighting device.

FIG. 9 is a graph showing two types of incident light intensity distributions and reflected light intensity distributions for each incident light.

FIG. 10 is a graph showing three types of incident light intensity distributions and a reflected light intensity distribution for each incident light.

FIG. 11 is a perspective view showing the configuration of the entire surface inspection apparatus of another embodiment.

FIG. 12 is a perspective view showing the configuration of the entire surface inspection apparatus of another embodiment.

[Explanation of symbols]

1: Steel plate 2, 2B, 2C, 2D, 2E: Illumination device 3, 6: Line sensor camera 3B, 6B: Pipe receiver (optical rod + photomultiplier tube) 4: Abnormality determination circuit 5: Light emission port 7, 8: Signal processing circuit 21, 22: Illumination mechanism 23, 24, 28: Lens 25: Laser light source 26: Hafmylar 27: Reflector 29: Scanning mechanism 51, 52: Opening 61: Engagement part 62: Spacers 205, 206, 207: Shading plates 208, 209, 210: Shafts 211, 221: Fluorescent lamps 212, 222: Parabolic mirrors 213, 223: Diffusing plates 214, 224: Variable diaphragm mechanisms 215, 217, 225, 227: Light-shielding plate 291: Polygon mirror 292: Reflecting mirror Wsa, Wsb: Slit width

Claims (6)

[Claims] 1. An illuminating device for irradiating the surface of an inspection object with light, a light receiving device installed in the direction of specular reflection of the light with which the inspection object is irradiated, and light depending on the light incident on the light receiving device. A surface inspection apparatus comprising an identification device for identifying a surface state of the inspection object: a substantially identical inspection of the surface of the inspection object from two positions adjacent to the lighting device at a distance from each other. A surface inspection apparatus comprising an illumination mechanism for irradiating illumination light toward a position. 2. The illumination mechanism comprises two slit-shaped openings installed at positions adjacent to each other, at least one light source for radiating light toward these openings, and between the light source and the opening. The surface inspection apparatus according to claim 1, further comprising a diffusion plate installed on the surface. 3. The illumination mechanism includes a slit-shaped opening,
Two lighting units having a light source for irradiating light toward the opening and an optical lens arranged between the light source and the opening are installed at positions adjacent to each other, and these two lighting units are provided. The surface inspection apparatus according to claim 1, wherein the optical axes of the illumination light are arranged so as to be inclined with respect to each other. 4. The illumination mechanism comprises one light source for emitting a beam of light and a beam for separating a single light beam emitted from the light source into two light beams. Separation mechanism and the beer
The surface inspection apparatus according to claim 1, further comprising an optical lens disposed in a path of two light beams emitted from the beam separating mechanism. 5. The surface inspection according to claim 1, claim 2, claim 3, or claim 4, wherein the illumination mechanism includes a variable diaphragm mechanism installed between the light source and the light exit port. apparatus. 6. The movable mechanism for supporting at least the position of the diaphragm mechanism of the illumination device so as to be movable with respect to the optical axis direction of the illumination light. 4. The surface inspection device according to 4.