JP2001281155A - Line inspection device for metal surface defect - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent deterioration in detection accuracy by uniformly illuminating an illumination spot line of a specified width on a metal surface with an equal amount of light for every part to avoid irregular illumination. SOLUTION: Condensing lenses 13 or condensing reflectors 14 are disposed on an optical path between a halogen lamp 9 and the metal surface, a surface 5 of an extruded aluminum section. The lenses 13 or the reflectors 14 condense a light flux emitted from a light source, the lamp 9, into a uniform light flux having a specified width, emit it to the surface 5, and focus regular reflection light therefrom to a point. A line sensor 10 is provided for highly resolving the reflection light flux of a specified width reflected by the surface 5 of the aluminum section. A focusing lens 11 for focusing the reflection light flux of the specified width onto the line sensor 10 is disposed on an optical axis on which the reflection light flux of the specified width is focused to the point between the line sensor 10 and the metal surface.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a metal surface defect line inspection apparatus for detecting defects generated on a metal surface, for example, the surface of an extruded aluminum material by using an optical method.

[0002]

2. Description of the Related Art Extruded aluminum materials are widely used as building materials such as sashes, and not only have their cross-sections become more complex, but they have also been developed in various specifications, such as changing the color and gloss of the surface finish. Mass-produced. In the aluminum extrusion process, an aluminum material called a billet is heated and formed into a predetermined shape through an extruder.Small scratches may occur on the aluminum surface when passing through a die frame that determines this shape . Only after entering the next alumite processing and coloring step, the flaw becomes glossy and uneven coloring and becomes a subject of claims. When such a defect occurs, the entire lot must be re-created again, and aluminum section manufacturers have suffered significant economic and time losses.

[0003] Inspection of the surface defects of extruded aluminum bars still relies on visual inspection, and there is a veteran who performs a product inspection one by one on each extruding machine side. In addition, oversight is more likely to occur as the scratches become finer. Also, in the current sampling inspection after the end of the extrusion process, even if a defect is found, re-creation is inevitable, and unless an in-line inspection is performed at an early stage of the process, it does not contribute to an improvement in productivity. Despite the recent emphasis on quality control of the surface of aluminum profiles, the use of FA and IT in defect inspection techniques has remained as an unexplored field.

[0004] Conventional metal surface defect detection techniques can be roughly classified into a contact method and a non-contact method. The former is a classic method represented by the stylus type, and it cannot be used for soft materials such as aluminum because the surface is damaged in reverse. The latter include a gloss meter and a surface defect inspection method using laser scattering described in a laser measurement handbook (issued on September 25, 1993 by Maruzen Co., Ltd.) (for example, Kawatetsu technique, 18, No. 2). , P. 115 (1986), iron and steel, 70, No. 9 (1986)). However, since all the measurement spots are small, some kind of scanning means is required to examine the entire profile. In the method of measuring the distribution range of scattered light in two dimensions, analysis takes time,
To implement in-line inspection, a new method had to be developed.

[0005]

A general aluminum profile has a width of about 5 to 20 cm, and a high spatial resolution is required to detect a dice mark of several tens of microns that can be discerned by the naked eye. Is required. In addition, since the speed of a profile extruded from a machine in an actual process reaches as much as 1 m per second, a considerably high-speed signal processing technique is required. Only when these problems can be overcome, in-line inspection becomes possible.

In view of the field of in-line inspection, an optical method capable of non-contact measurement and high-speed processing is optimal.
In the visual inspection, while observing the surface of the aluminum, if the image of the distant light source is brightly reflected and seen, the surface is determined to be smooth, and if a dark streak-like line is seen, it is determined that there is a scratch there. This utilizes a phenomenon in which the amount of specularly reflected light (also referred to as specularly reflected light) decreases due to the roughening of the metal.

[0007] In order to make this method FA, the light scattering phenomenon by the extruded material will be examined in more detail. As shown in FIG. 1, a parallel light flux 1 illuminates a metal surface 2 at an incident angle θ, and considers a light amount distribution of a spot projected on a screen 3 placed in a regular reflection direction (reflection angle θ). Metal surface 2 as shown in FIG.
Is nearly a smooth mirror surface, a small spot 4 is generated near the center of the screen due to regular reflection. The light intensity distributions on the x and y axes in the figure are shown in FIGS. 2 (a) and 2 (b), respectively.
It changes like The height of the light intensity distribution, which is a measure of the absolute value of the light intensity distribution, decreases.

On the other hand, when the aluminum extrusion 5 is illuminated as shown in FIG. 3, a direction (x-axis) perpendicular to the extrusion direction (y-axis) is obtained.
Spots 6 caused by scattered light extending in the x-axis direction around the spot 4 of specularly reflected light due to the fine surface irregularities generated
Appears. The light intensity distribution in the x and y axis directions at this time is shown in FIG.
As shown in (a) and (b), on the x-axis plane of the direction, the scattered light overlaps the two components of the strong peak near the origin and the widely distributed base corresponding to the unevenness of the metal surface 5. become.
Further, since there is almost no unevenness in the extrusion direction, the light flux does not spread in the y-axis direction, and a sharp peak due to only a specular reflection component close to an almost smooth mirror surface similar to the metal surface 2 shown in FIG. 1 appears. In the case of a non-defective product having no scratch on the surface, such a light amount distribution is usually obtained.

On the other hand, as shown in FIG. 5, when a deep flaw called a dice mark is made on the aluminum surface, light is scattered at this location (that is, the flaw is two-dimensionally formed on the x and y axes). Because of its presence, the specularly reflected light spot (observed on the flawless x-axis in FIG. 3) disappears, leaving only the scattered light spot 6 as shown. As shown in FIGS. 6 (a) and 6 (b),
It can be seen that the center regular reflection peak disappears in the distribution in the x and y axis directions. The difference in the spread of the scattered light distribution between FIG. 6A and FIG. 6B is that the width of the flaw in the x-axis direction is wider than the width of the flaw in the y-axis direction. This is because the tail of the light distribution is widened.

When a streak 8 is formed on the aluminum surface as shown in FIG. 7, this portion is roughened in the extrusion direction, so that no spot of specular reflection light is generated on the screen, and a spot of scattered light 6 is formed. Only. The distribution of the scattered light also spreads in both the x and y axes as shown in FIGS. 8 (a) and 8 (b). The spread of the scattered light distribution in FIGS. 8A and 8B is exactly the same for the same reason as described with reference to FIG. That is, FIG.
This is because the width of the flaw in the x-axis and y-axis directions is the same in the case of (1).

When inspecting a surface defect visually, such a light scattering characteristic is utilized. A distant light source is projected on an aluminum surface, light is scattered by a scratch, and regular reflection light is attenuated. The degree of darkening is used as a criterion. As shown in FIG. 9, light from a halogen lamp 9 as a light source is uniformly illuminated at an appropriate angle θ toward the profile surface, and an aluminum surface is observed with a high-resolution line sensor 10 placed in the regular reflection direction. It is only necessary to detect the depression of the specular reflection light due to the scratch.

However, as shown in FIG. 9, when the aluminum extruded material surface 5 is illuminated with the light beam spread from the halogen lamp 9, the central portion of the light beam is specularly reflected and passes through the imaging lens 11, but the irradiation spot line Light that illuminates the periphery of the mirror 12 and is specularly reflected does not pass through the lens 11. Therefore, when such a light source is used, the output signal of the line sensor is as shown in FIG.
Although the center is high like 0, it is low at both ends, and the detection accuracy decreases.

SUMMARY OF THE INVENTION The present invention has been made in view of the above problems, and has been made in order to solve the problems. It is an object of the present invention to make the same light amount uniform on an irradiation spot line having a predetermined width on a metal surface. It is an object of the present invention to provide a metal surface defect line inspection apparatus capable of avoiding irradiation unevenness and preventing a decrease in detection accuracy.

[0014]

In order to achieve the above object, the present invention converges a light beam emitted from a light source into a uniform light beam having a predetermined width, radiates the light beam on a metal surface, and specularly reflects the light at one point. A condensing lens or a condensing reflector for forming an image is arranged on the optical path between the light source and the metal surface, and a line sensor for highly resolving a regular reflection light beam having a predetermined width reflected on the metal surface is provided. The optical system comprises means for arranging an image forming lens for forming an image of a specularly reflected light beam having a predetermined width on a line sensor on an optical axis for forming an image of the specularly reflected light from the metal surface at one point.

[0015]

DESCRIPTION OF THE PREFERRED EMBODIMENTS In other words, in order to overcome the above-mentioned drawbacks, an optical system as shown in FIGS. 11 and 13 has been devised.
In the drawing, a condenser lens 13 (see FIG. 11) or a condenser reflector 14 (see FIG. 13) is provided on an optical path between, for example, a halogen lamp 9 as a light source and an extruded aluminum material surface 5 as a metal surface. ) Is arranged.

The condensing lens 13 or the condensing reflector 14 converges a luminous flux from, for example, a halogen lamp 9 as a light source into a uniform luminous flux having a predetermined width and radiates the luminous flux on, for example, an extruded aluminum material surface 5 as a metal surface. And the specularly reflected light
It is arranged at a position where an image is formed on a point.

The radiated light radiated from the light source in the width direction of the extruded aluminum material surface 5 is collected by the condenser lens 13 or the condenser reflector 1.
4, the light beam is converted into a uniform light beam having a predetermined width, that is, the same light amount, and is irradiated onto, for example, an irradiation spot line 12 in the entire width range of the extruded aluminum material surface 5, and irradiation unevenness on the irradiation spot line 12 is reduced. Be avoided.

Further, the radiated light emitted from the light source in the width direction of the extruded aluminum surface 5 is condensed by a condenser lens 13 or a condensing reflector 14 onto an irradiation spot line 12 having the entire width of the extruded aluminum surface 5. After being reflected by, an image is formed at one point. An imaging lens described later is disposed at this point.

In this case, when the condensing lens 13 is used, the light source is disposed in a space above the surface 5 of the extruded aluminum member, and the condensing lens 13 is disposed between the light source above and the surface 5 of the extruded aluminum member 5. And the space between them.

Further, when the condensing reflector 14 is used,
The light source is located at a position other than the space above the aluminum extrusion surface 5,
For example, it can be arranged at the upper side or at the same height as the surface of the extruded aluminum material 5, and the degree of freedom of the arrangement position of the light source is increased.

The line sensor 10 is a device for performing high-resolution specular reflection light of a predetermined width reflected on a metal surface, for example, the aluminum extruded profile surface 5, and above the aluminum extruded profile surface 5, for example. It is provided in parallel with the width direction.

On the optical axis where the specular reflection light between the line sensor 10 and the surface of the extruded aluminum material 5 as a metal surface is imaged at one point, a specular reflection light beam having a predetermined width is applied to the line sensor 10. An imaging lens 11 for forming an image is arranged. The imaging lens 11 is arranged in a space between the upper line sensor 10 and the surface 5 of the extruded aluminum material.

The optical system described above allows the light source, for example, a halogen lamp 9 (or a high luminance L (not shown)).
The light emitted from the ED) is converted by a condenser lens 13 into a uniform focused light beam having a predetermined width and the same light amount, which is applied to a full width irradiation spot line 12 on a metal surface, for example, an aluminum extruded material surface 5. After the reflection, only the regular reflection light passes through the imaging lens 11 and is detected by the line sensor 10. As a result, the output signal level of the line sensor 10 becomes
As shown in FIG. 12, all pixels on the irradiation spot line 12 become almost uniform, and sensitivity unevenness can be suppressed. The function of illuminating with such condensed light can also be realized by a converging / reflecting mirror 14 such as a spherical mirror as shown in FIG.

If a high-magnification lens is used as the imaging lens 11, even a fine scratch that is difficult to determine with the naked eye can be detected from a decrease in the amount of specularly reflected light. In that case, the detection length becomes short, so that the detection head incorporating the light source, the imaging system, and the line sensor 11 is mounted on the stage, and the measurement is performed while moving at right angles to the extrusion direction, and the partially obtained data is connected. Can be solved. In the case of in-line measurement, since the profile moves at high speed, there is a possibility that vibration due to vibration or the like may occur. In that case, halogen lamp 9
Can be solved by using strobe light emission by a xenon discharge tube or the like, or by using an electronic shutter on the line sensor 11 side.

[0025]

FIG. 14 shows an embodiment of the apparatus according to the present invention. A luminous flux from, for example, a halogen lamp 9 as a light source is condensed as an irradiation spot line 12 on an aluminum extruded profile surface 5 by a condensing lens 13 and is focused by an imaging lens 11 placed on an optical axis of specularly reflected light. , An irradiation spot line 12 on the surface 5 of the extruded aluminum material is connected to a high-resolution line sensor 10.
Image on top. These components are mounted inside the inspection head housing 15. The inspection head housing 15 is attached to an XYZ stage or a robot arm, and is installed above the surface 5 of the extruded aluminum material.

When used for in-line inspection, the non-inspection surface itself moves, so that driving in the Y-axis direction becomes unnecessary. Driving in the Z-axis direction is required for focusing the inspection head.
In addition, the inspection head can be tilted from the vertical plane by an angle φ corresponding to the case where the non-inspection surface is inclined. Further, if the incident angle of the light beam and the regular reflection angle θ (2θ in FIG. 1) are changed, the detection sensitivity of the flaw can be changed to some extent. Therefore, such an adjustment mechanism is also provided in the inspection head.

Instead of, for example, the halogen lamp 9 as a light source, a large number of high-brightness LEDs 16 are radiated toward a diffusion plate 17 disposed at a predetermined position between the high-brightness LED 16 and the condenser lens 13 as shown in FIG. However, it can be used as a secondary light source. In this case as well, a 13
When the light is focused on the surface 5 of the extruded aluminum material, the regular reflection light is uniformly projected on the line sensor 10, and the same result as that of FIG. 14 is obtained.

[0028]

The defects on the metal surface cause various troubles in the subsequent steps. For example, surface defects generated in the aluminum extrusion process appear as uneven gloss and coloring in the next surface finishing process. In such a situation, the lot would have to be re-created again, with significant economic and time losses. In recent years, product quality control has become one of the most important issues, and improvement of in-line inspection technology is becoming essential. Conventional inspection items such as mechanical strength are of course important, but aesthetic inspection items such as fine scratches and gloss on the surface are also inevitable issues, and the establishment of inspection techniques is required.

By using the system according to the present invention, surface defects can be automatically detected at the initial stage of production in metal processing, for example, in the process of extruding thousands of types of aluminum shapes, so that die exchange and the like can be performed. By reworking the dice, etc.
Useless processes can be minimized. This directly leads to faster production processes and energy savings, leading to a dramatic improvement in productivity and a reduction in production costs. The visual inspection process is no longer necessary, and labor costs can be saved. In addition, since the quantification of surface defects becomes possible, it can be expected that it will be fed back to the die design technology and contribute to the technological innovation of the entire extrusion process.

[Brief description of the drawings]

FIG. 1 is an explanatory diagram showing a distribution of light reflection from a smooth metal surface.

FIG. 2 is a diagram showing a light amount distribution along an x-axis (a) and a y-axis (b) on a screen 3 of FIG.

FIG. 3 is an explanatory diagram showing a distribution of light reflection from the surface of an aluminum profile.

FIG. 4 is a view showing a light quantity distribution along an x-axis (a) and a y-axis (b) on the screen 3 of FIG.

FIG. 5 is an explanatory diagram showing a distribution of reflected light when a deep dice mark is formed on the surface of an aluminum profile.

FIG. 6 is a view showing a light amount distribution along an x-axis (a) and a y-axis (b) on the screen 3 of FIG.

FIG. 7 is an explanatory diagram showing a reflected light distribution when a streak is present on the surface of an aluminum profile.

8 is a diagram showing a light quantity distribution along an x-axis (a) and a y-axis (b) on the screen 3 in FIG.

FIG. 9 is an explanatory view showing an example in which an aluminum profile is directly illuminated by a light source.

FIG. 10 is an explanatory diagram showing that the output distribution of the area sensor of FIG. 9 is not uniform.

FIG. 11 shows an embodiment of the present invention, in which a condensing lens is used and an aluminum profile is installed in the middle of an optical path for converging emitted light from a light source toward a stop of an imaging lens. FIG.

FIG. 12 illustrates an embodiment of the present invention, and in the case of FIG. 11, specularly reflected light efficiently passes through an imaging lens;
It is explanatory drawing which showed that the output of an area sensor became flat.

13 is a view showing an embodiment of the present invention, and is an explanatory view showing that specularly reflected light can be similarly collected on an imaging lens by using a spherical mirror instead of a condenser lens in FIG. 12. FIG. is there.

FIG. 14, which shows an embodiment of the present invention, is an explanatory view showing an embodiment of an apparatus for in-line inspection of surface defects of aluminum profiles.

FIG. 15 shows an embodiment of the present invention, and FIG.
This is an embodiment of a secondary light source using a high-brightness LED and a diffusion plate instead of a halogen lamp.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Parallel light flux 2 Smooth metal surface 3 Screen 4 Regular reflection spot 5 Extruded aluminum material surface 6 Spot where scattered light spread 7 Deep scratch on aluminum surface 8 Streak 9 Halogen lamp 10 Line sensor 11 Imaging lens 12 Irradiation spot line 13 Condensing lens 14 Condensing reflector 15 Inspection head housing 16 High brightness LED 17 Diffusion plate

 ──────────────────────────────────────────────────続 き Continued on the front page F term (reference) 2F065 AA49 BB05 BB13 BB15 CC00 DD06 FF42 GG02 GG07 GG12 HH04 HH05 HH12 HH17 JJ03 JJ08 JJ25 LL04 LL08 LL19 MM03 PP04 PP05 PP25 2G051 AA11 CB09 BB09 BB09 CB09

Claims (2)

[Claims] 1. A light-collecting lens or a light-reflecting mirror for converging a light beam emitted from a light source into a uniform light beam having a predetermined width, radiating the light beam on a metal surface, and forming an image of specular reflection light at one point. An optical axis is arranged on the optical path between the line sensor and a line sensor for highly resolving a regular reflection light beam of a predetermined width reflected on the metal surface, and forms an image of the regular reflection light between the line sensor and the metal surface at one point. A metal surface defect line inspection apparatus, further comprising an imaging lens for imaging a regular reflection light beam having a predetermined width on a line sensor. 2. The metal surface defect line inspection apparatus according to claim 1, wherein a diffusion plate is disposed at a predetermined position between the high-brightness LED as a light source and the condenser lens or the condenser mirror.