JP2643550B2 - Appearance inspection device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a visual inspection device capable of accurately inspecting a work having a glossy surface, for example, a stain adhered to a surface of a lid of a beverage can, based on an image taken.

[Prior art]

A conventional example will be described with reference to FIG. 3 which is a side view thereof. In the figure, reference numeral 9 denotes a lid of a beverage can as a target work, and reference numeral 11 denotes a camera. Reference numeral 7 denotes a single light source. Although only two light sources are shown in the figure, a plurality of light sources are generally arranged outside the cylindrical filter 12. Of course, instead of a plurality of single light sources 7, one annular light source may be used. The frusto-conical cylindrical filter 12 has a light-diffusing and transmissive property, and its axis is inclined so as to form an angle θ with a normal set on the surface of the work 9. The optical axis of the camera 11 is substantially coincident with the axis of the cylindrical filter 12. Therefore, the operation of the appearance inspection apparatus is as follows. Irradiation light from a plurality of single light sources 7 from outside the periphery of the cylindrical filter 12 is diffused by passing through the cylindrical filter 12 to irradiate the surface of the work 9 from all directions. . In addition, since the axis of the cylindrical filter 12 and thus the optical axis of the camera 11 are inclined with respect to the normal set on the surface of the work 9, the camera 11 has its own reflection image on the surface of the work 9. Is not incident.
As a result, an accurate image over the entire surface of the work 9 can be obtained, and an appropriate and effective appearance inspection of the degree of dirt can be performed.

[Problems to be solved by the invention]

The conventional technique described above has a drawback that the optical axis of the camera is inclined with respect to the normal to the work surface, so that the captured image of the work surface is distorted and the inspection becomes inaccurate accordingly. As a countermeasure against this drawback, if the camera's optical axis is made to coincide with the normal to the work surface, the camera's objective distance must be set large enough so that the camera's own image reflected on the glossy surface of the work is not captured. There must be. Therefore, a telephoto lens is required for the camera, which results in an increase in cost. An object of the present invention is to solve the above problems of the prior art, and to accurately detect a stain on a work having a glossy surface, for example, a surface of a lid of a beverage can, based on an image taken. It is an object of the present invention to provide a visual inspection device capable of performing an inspection and achieving a reduction in size and cost.

[Means for Solving the Problems]

In order to solve this problem, a visual inspection apparatus according to the present invention is an apparatus for imaging a work having a glossy surface from directly above and inspecting the surface for dirt based on the image. A first hole coaxial with the optical axis of the imaging device, the first hole being coaxial with the optical axis at the position intersecting the optical axis for imaging, and allowing the external illumination light to diffusely pass therethrough; A dome-shaped wall that diffusely reflects on the surface; a second hole having a diffuse reflection surface on a side of the wall facing the surface near the first hole and coaxial with the optical axis and smaller than the first hole; A reflecting plate opened as an aperture.

[Action]

In the appearance inspection apparatus according to the present invention, the external illumination light becomes diffused light after passing through the dome-shaped wall and irradiates the work surface uniformly from all directions. In addition, part of the external illumination light is diffusely reflected on the surface near the first hole of the wall, passes through the first hole after being diffusely reflected again by the reflector, and irradiates the work surface as diffused light. . Therefore, the shadow of the reflection plate reflected on the work surface is imaged as a uniformly bright (white) surface. Furthermore, since the diameter of the second hole is small, the shadow of the imaging means reflected on the work surface is narrowed down and has almost no size. As a result, the picked-up image of the work surface does not cause halation and accurately represents the state of the work surface.

【Example】

An embodiment of a visual inspection apparatus according to the present invention will be described below with reference to the drawings. FIG. 1 is a side view of this embodiment. In the figure,
1 is a camera, 2 is a neutral density filter, and is provided in front of the camera 1. Reference numeral 3 denotes a reflection plate that diffusely reflects incident light, and is provided in front of the neutral density filter 2. The reflection plate 3 is made of a milky white plastic plate, and is formed by attaching an aluminum film to the surface on the side of the neutral density filter 2. This reflector 3
Corresponds to the second hole in the invention. Hole 3a as aperture
Are aligned with the optical axis of the camera 1. Reference numeral 5 denotes a wall of a dome-shaped plate-like member, which diffusely transmits external illumination light from a plurality of single light sources 7 and transmits external illumination light on a surface near a location facing the reflector 3. Diffusely reflected. In addition, a hole 5a corresponding to the first hole in the present invention is formed at a position intersecting with the optical axis of the camera 1 in the upper part of the wall body 5. The hole 5a is a hole of the reflector 3.
Greater than 3a. The wall body 5 is formed by molding a milky white plastic plate into a dome shape, and is treated so as to diffuse and reflect external illumination light particularly on the surface near the upper hole 5a. Reference numeral 9 denotes a work to be inspected, which is a metal lid having a glossy surface. The work 9 is placed on an unsigned inspection table such that the surface is substantially perpendicular to the optical axis of the camera 1, and has a shape surrounded by the wall 5. The operation of this embodiment will be described with reference to FIG. 2 which is a schematic cross-sectional view of the main part. In the figure,
After the external illumination light from the light source 7 passes through the dome-shaped wall 5, it becomes diffused light as shown in the figure, and uniformly illuminates the work surface (not shown) from all directions. Further, a part of the external illumination light is diffusely reflected on the surface near the hole 5a of the wall 5 as shown in the drawing, and irradiates the reflector 3 and diffuses and reflects here again, and then passes through the hole 5a. And irradiates the work surface as diffused light. Therefore, the shadow of the reflector 3 reflected on the surface of the work is captured by the camera 1 as a uniformly bright (white) surface. Further, the shadow of the camera 1 reflected on the work surface is reflected by the reflector 3.
Since the diameter of the hole 3a is small, it is squeezed and has almost no size. In this embodiment, the hole 3a has a diameter of 1 to 2 mm,
The hole 5a is designed to have a diameter of 20 to 30 mm and a distance between the upper surface of the wall 5 and the lower surface of the reflector 3 of 15 mm. As a result, the picked-up image of the workpiece surface does not cause halation, regardless of the glossiness of the workpiece surface, and can accurately represent the state of the workpiece surface.

【The invention's effect】

In the present invention, the external illumination light becomes diffused light after passing through the dome-shaped wall, and uniformly irradiates the work surface from all directions;
Since the light is diffusely reflected on the surface near the hole and then diffused and reflected again by the reflector, the light passes through the first hole and is scattered to irradiate the work surface. Therefore, the shadow of the reflector reflected on the work surface is uniform. The image is picked up as a bright or white surface; the shadow of the imaging means reflected on the surface of the work is narrowed down and has little size since the diameter of the second hole is small. Therefore, according to the present invention, the following excellent effects are obtained as compared with the related art. (1) The picked-up image of the work surface does not cause halation and accurately represents the state of the work surface, so that the dirt attached to the work surface can be inspected accurately. (2) Since the imaging means is located directly above the work and it is not necessary to increase the object distance, the appearance inspection device can be miniaturized. (3) Since the imaging means is located directly above the work, the image of the imaged work surface is not distorted and the inspection becomes more accurate as compared with the case where the imaging means is positioned obliquely as in the conventional example. (4) In the conventional method in which the imaging means is positioned directly above the workpiece, the object distance must be set large so as not to capture the shadow of the imaging means itself reflected on the work surface. Although a lens is required, a normal lens may be used according to the present invention, and the cost can be reduced accordingly.

[Brief description of the drawings]

 FIG. 1 is a side view of an embodiment according to the present invention, FIG. 2 is a schematic sectional view of a main part showing the operation of this embodiment, and FIG. 3 is a side view of a conventional example. Description of symbols 1: camera, 2: neutral density filter, 3: reflector, 3a: hole (second hole), 5: wall, 5a: hole (first hole), 7: light source, 9: work.

Claims (1)

(57) [Claims] An image of a work having a glossy surface is taken from directly above,
In a device for inspecting the surface for dirt based on the image, a first device is installed so as to surround the work placed on an inspection table, and is coaxial with a position intersecting with an optical axis for imaging. A dome-shaped wall having a hole, which diffusely transmits external illumination light, and diffusely reflects on the surface near the first hole; and diffusely reflects on a side of the wall facing the surface near the first hole. A reflecting plate having a surface and coaxial with the optical axis and having a second hole smaller than the first hole formed as a stop.