JPH04178541A - Illuminating device for checking appearance - Google Patents

Abstract

PURPOSE:To visually confirm a defective portion of the surface of an article easily and correctly by applying light rays in various directions extending over a wide range to the surface of an article by one curved surface light source body and a semispherical light source body. CONSTITUTION:Light rays generated from a curved surface light source body 1 irradiate the surface of an article 11. When a defective portion 12 such as a flaw or the like exists in the surface of the article 11, the defective portion 12 are illuminated by the light rays applied from the light source body, so that the brightness is different from that of a portion where there is no defective portion 12. Thus, the existence of a defective portion can be recognized by observing the surface of the article 11 to find a portion with different brightness. In case of checking the defective portion 12, the defective portion 12 is made rise to the surface by applying light of specified angle corresponding to the length, width and depth thereof. Thus, the defective portion 12 existing in the surface of the article 11 is illuminated by light of the light source body 1 so as to be visually confirmed easily and correctly.

Description

DETAILED DESCRIPTION OF THE INVENTION [Object of the Invention] (Industrial Application Field) The present invention relates to an illumination device that irradiates a light beam onto an article when observing the appearance of the article and inspecting the surface condition thereof.

(Prior Art) As a method for inspecting defects such as scratches existing on the surface of an article such as a metal plate or a metal bar, there is an appearance inspection method in which the appearance of the article is observed and the surface condition is inspected. Observation methods used in this visual inspection method include directly observing the surface of the product with the human eye, and using a television camera to photograph the surface of the product and displaying the image on a monitor, which the inspector then observes by looking at the monitor image. can be given.

In this inspection method, in order to easily and reliably discover defects present on the surface of the article, it is necessary to irradiate the surface of the article with a light beam using an illumination device. That is, when a light beam is irradiated onto the surface of an article, the presence of scratches can be clearly seen because the brightness differs between parts of the surface with and without scratches.

Conventionally, illumination devices used for external observation methods use tungsten lamps, halogen lamps, fluorescent lamps, etc. as light sources, and bright field coaxial illumination methods (as shown in Figures 4 to 7)
), oblique illumination method (Fig. 5), specular illumination method (Fig. 6)
, ambient-like illumination (FIG. 7), and other illumination methods are employed. Note that in the figure, a indicates an article, and b indicates an observation television camera.

(Problems to be Solved by the Invention) However, such conventional lighting devices for visual inspection have the following problems.

In the bright field coaxial illumination method, oblique illumination method, and specular reflection illumination method, there is a limit to the number of defects that can be detected on the surface of the article under the light rays emitted from the light source, resulting in defects being overlooked. Sometimes.

For this reason, during visual inspections, the object is repositioned or oriented in relation to the light emitted from the light source in order to detect more flaws, but defects may still be missed. At the same time, a lot of time and effort is required for visual inspection.

Furthermore, there is a limit to the size of the irradiation range of one light source, making it difficult to irradiate a wide range with a light beam at a constant illuminance.

The present invention has been made based on the above-mentioned circumstances, and is used for appearance inspection, which allows defects present on the surface of an article to be easily and reliably seen by irradiating the surface of the article with light beams in various directions over a wide range. The purpose is to provide lighting equipment.

[Structure of the Invention] (Means and Effects for Solving the Problems) The present inventor has solved the problem that in conventional illumination devices for appearance inspection, only a part of the defective part existing on the surface of the article can be visually recognized by the light beam of the light source. I have conducted various research.

As a result, we found the following.

The defects present on the surface of the article vary in length, width and depth. This defective portion can be highlighted so that it can be easily and reliably visually recognized by a light beam incident from a direction corresponding to its shape, that is, its length, width, and depth.

In other words, if the light beam that irradiates the surface of the article is only in a specific direction, the defect that is irradiated by this light beam and clearly stands out as a defective area corresponds to the direction of the light beam. It is difficult to highlight defects that are limited to a specific shape and have other shapes so that they can be easily and reliably seen with the light beam in the above-mentioned direction.

However, in the bright field coaxial illumination method, the oblique illumination method, and the specular reflection illumination method, a single light source irradiates the article with a light beam from a specific direction depending on the position of the light source. For this reason,
With these illumination methods, there is a limit to the number of defects that can be found on the surface of an article under the light beam irradiated from a particular direction for the reasons mentioned above.

As a countermeasure to this, by irradiating the surface of the article with light beams in various directions at once, it is possible to clearly highlight various types of defective parts so that they can be visually recognized by the light beams in each direction. In order to irradiate the surface of the article with light beams in various directions at once, it is possible to irradiate the surface of the article using a plurality of light sources. However, this requires a large number of light sources, which is very uneconomical.

Therefore, in order to solve such problems, the present inventors focused on a light source body having a curved light emitting surface, a hemispherical light emitting surface, or a spherical light emitting surface. In a light source body having a curved light emitting surface, a hemispherical light emitting surface, or a spherical light emitting surface, light rays can be emitted from each position of the light emitting surface in different directions. In addition, a light source with a curved light-emitting surface, a hemispherical light-emitting surface, or a surface light source with a spherical light-emitting surface illuminates the surface of the article with light rays in various directions at once from the light-emitting surface. It becomes easy to irradiate a wide range of light beams with constant illuminance.

Therefore, by using a light source with a curved light-emitting surface, a hemispherical light-emitting surface, or a surface light source with a spherical light-emitting surface, the position and orientation of the product can be varied in various ways during the visual inspection of the product. It is not necessary to use a large number of light sources to illuminate the article, and it is possible to clearly highlight various types of defects on the surface of the article and easily and accurately see them. I can do it.

The present invention has been made based on this knowledge.

That is, in the lighting device for appearance inspection of the present invention, in a lighting device that irradiates a light beam to an article when observing the appearance of the article and inspecting the surface condition, a panel whose negative side is the light-emitting surface is used as the light-emitting surface. It is characterized by comprising a curved light source body, a hemispherical light source body, or a spherical light source body that is curved so that the surface is on the inner peripheral side.

Each light source uses a light source that has light distribution in the forward direction of irradiation, and its shape is not limited in any way as long as it has such characteristics. Further, the light source is not limited in any way, but examples include those using electroluminescence or those using a large number of light emitting diodes.

(Example) Hereinafter, an example of the present invention will be described with reference to the drawings.

An embodiment of the lighting device for visual inspection of the present invention will be described with reference to FIGS. 1 to 3. This embodiment uses a curved light source as the light source.

The configuration of the lighting device for visual inspection of the present invention will be explained.

In the figure, 1 is a curved light source, and 2 is a support that supports the curved light source 1.

The light source of the curved surface light source body 1 uses electroluminescence. The electroluminescent curved light source 1 is shaped like a panel made up of a back electrode layer, a dielectric layer, a phosphor layer, a transparent electrode layer, etc. It is a surface light source that emits . This electroluminescence is flexible and has a shape that is curved in the vertical direction with a predetermined radius of curvature with the light emitting surface inside. Note that the size of the curved surface light source body 1 is set depending on the size of the article to be compared.

A case in which the appearance of an article is inspected using this illumination device will be described.

When inspecting the appearance of an article, first, the curved surface light source body 1 is energized and turned on. The curved surface light source 1 emits light over the entire surface of the panel due to the light emitting action of electroluminescence. The curved surface light source body 1 is curved along the vertical direction, and has a light emitting surface on its inner peripheral surface. Therefore, at each position from the upper end to the lower end in the curved direction of the light emitting surface, light rays are emitted along a direction corresponding to each position. The light rays emitted at each position from the upper end to the lower end in the curved direction are focused on a defined focal point corresponding to the curvature of the light emitting surface.

The surface of the article 11 is irradiated with light rays emitted from the curved light source 1. When a defect 12 such as a scratch exists on the surface of the article 11, the portion of the defect 12 is illuminated by the light rays emitted from the curved surface light source 1, and the brightness is reduced compared to the portion without the defect 12. (brighter or darker). Therefore, by observing the surface of the article 11 and finding areas where the brightness is different, it is possible to recognize the presence of the defective portion 12 on the surface of the article 11.

For example, a television camera 3 is used to observe the surface of the article 11.
use. The television camera 3 uses a solid-state imaging device and photographs the surface of the article 11 through a close-up ring 4 and a zoom lens 5. The image taken by the television camera 3 is displayed on the monitor 6. This image is an enlarged view of the surface of the article. The inspector looks at the image displayed on the monitor 6, observes the surface condition of the article 11, and inspects the presence of a defective part 12.

Here, inspection of the defective portion 12 existing on the surface of the article 11 will be explained.

The defective part (uneven part) 12 existing on the surface of the article 11 has a length,
They have different widths and depths. Since the light emitting surface of the curved surface light source 1 is curved in the vertical direction, light rays are emitted at each position from the upper end to the lower end in the curved direction of the light emitting surface along a direction corresponding to that position.

That is, the curved surface light source body 1 irradiates the surface of the article 11 with light in various directions. As shown in FIGS. 2 and 3, the defective portion 12 existing on the surface of the article 11 is irradiated with light in a specific angular direction according to the length, width, and depth of the defective portion 12, and is raised. climb. In other words, light in various directions emitted from the light emitting surface of the curved surface light source 1 irradiates each defective portion 12 having a shape corresponding to the direction of the light. In this way, each defect 12 of various forms existing on the surface of the article 11
is illuminated by the light beam of the curved surface light source 1 and stands out so that it can be easily and accurately visually recognized.

Further, the curved surface light source 1 is a surface light source, and irradiates light over a wide range of the surface of the article 11 with a constant illuminance.

Therefore, the curved surface light source 1 can irradiate a wide range of the surface of the article 11 with light beams at once, and highlight many defective parts 12 of different shapes existing on the surface so that they can be easily and accurately seen. I can do it. Therefore, the inspector can easily and accurately discover many defective parts 12 having different shapes over a wide range while viewing the image of the surface of the article 11 displayed on the monitor.

When inspecting the appearance of the article 11, there is no need to variously change the position and orientation of the article 11, and there is no need to provide a large number of light sources to illuminate the article. Defects of various shapes can be clearly highlighted and visually recognized easily and accurately.

A specific example will be explained.

As a comparative example, the appearance of an article was inspected using a straight tube fluorescent lamp 7 as a light source, as shown in FIG. One 15W straight tube fluorescent lamp 7 was used. The article 11 is made of a nickel alloy and is rolled. Article 1
The number of 1's is 6.

The inspection method is to place the straight tube fluorescent lamp 7 at 30 degrees, 45 degrees, and 60 degrees with respect to the surface of the article 11.
The surface of each article 11 was irradiated to inspect the defective portion 12 present on the surface of each article 11.

The test results are shown in Table 1. In this table, a circle mark indicates that the defective part is clearly visible, a triangular mark indicates that the defective part is visible but difficult to see, and an X mark indicates that the defective part is not visible. According to this table, there are various types of defective parts, and depending on the angle of the light beam, the defective parts can be invisible or visible. Therefore, the reliability of visual inspection of articles is low. FIG. 8 shows this state.

Table 1 As an example of the present invention, the appearance of an article was inspected using a curved light source made of electroluminescence. The conditions of the article were the same as in the comparative example.

The test results are shown in Table 2. According to this table, it can be seen that the presence of defective parts can be visually recognized in all articles.

Table 2 The size of the defect that can be found in this comparative example is 3 μm in depth.
× Width 160μ is the limit, or in the example of the present invention, depth is 2μ
It has a 1X width of 43μ and has high inspection accuracy. Furthermore, in the comparative example, three fluorescent lamps were required in order to ensure an irradiation range that was the same size as the light irradiation range of the curved surface light source made of electroluminescence in the example of the present invention.

In the above-described embodiment, electroluminescence is used as a light source for the curved surface light source body, but the invention is not limited to this, and a surface light source with strong light distribution characteristics such as many light emitting diodes arranged in front of the irradiation direction may be used. A provided planar light source can be used.

The illumination device of the present invention can be used for visual inspection of a wide range of articles.

[Effects of the Invention] As explained above, according to the illumination device for appearance inspection of the present invention, light beams in various directions can be illuminated over a wide range of objects using one curved light source, hemispherical light source, or spherical light source. The surface of the article can be irradiated, defects on the surface of the article can be easily and reliably seen, and the appearance of the article can be easily and accurately inspected, thereby increasing economic efficiency.

As the light source of the light source body, one using a light source having a light distribution characteristic in the front in the irradiation direction, for example, one using electroluminescence, or one using a large number of light emitting diodes arranged in a row is suitable.

[Brief explanation of drawings]

FIG. 1 is a schematic configuration diagram showing an embodiment of the illumination device for visual inspection of the present invention, and FIGS. 2 and 3 show a state in which a curved surface light source body irradiates a light beam onto an article in an embodiment of the present invention. FIGS. 4 to 7 are diagrams showing examples of illumination methods, and FIG. 8 is a diagram showing an example of a state in which a light source irradiates a light beam onto an article in a conventional illumination device for visual inspection. 1... Curved surface light source body, 11... Article. Applicant's agent Patent attorney Takehiko Suzue 11 cases Nohonin Figure 1 Figure 4 Figure 5 Figure 6 Figure 7 Figure 8

Claims (2)

[Claims] (1) In a lighting device that irradiates a light beam onto an article when observing the appearance of the article and inspecting its surface condition, a panel having a light-emitting surface on one side is curved so that the light-emitting surface is on the inner peripheral side. An illumination device for visual inspection, characterized by comprising a curved light source, a hemispherical light source, or a spherical light source. (2) The illumination device for visual inspection according to claim 1, wherein the light source uses a light source having a light distribution characteristic in the forward direction of irradiation.