Device for inspecting the inner wall of a body

Abstract: The invention relates to the inspection of the inside of a body, for example the inner surface of a metal container (7) such as a preserves can. The best possible inspection is ensured with light­ ing from the same direction as that from which the inspection, for example with a video camera (1), takes place. The invention therefore provides a device for inspecting the inner surface of a hollow body such as a metal container with a cylindrical standing wall and a bottom, which device comprises: positioning means for placing the body at a chosen position; a light source (2) which is placed relative to the positioning means such that it can light the said inner sur­ face at least approximately uniformly; and an inspection means, for example a video camera (1), which is placed relative to the positioning means such that it can inspect the said inner surface, whereby the direction of lighting and the direction of inspection of each portion of the said inner surface at least approximately coincide.

Description: The invention relates to a device for inspecting the inner surface of a hollow body having a cylindrical standing wall and a bottom, said device comprising: positioning means for placing said body at a chosen position; a light source placed relative to said positioning means such that it can illuminate said inner surface; and inspection means, e.g. a video camera, placed relative to said positioning means such that it can view said inner surface; whereby the direction of lighting and the direction of inspection of each portion of the said inner surface at least approximately coincide. Thus, the direction of illumination and the direction of viewing each portion of said inner surface are substantially coincident. Such a device is known from US-A-3 150 266. According to this prior art reference a probe is inserted in a container to be inspected. By means of a periscope-like structure it is possible to determine at one axial level of the container a crack polution or other irregularity. By means of e.g. a helix-shaped scanning operation or the like the full inner surface of the container can be inspected. It is a purpose of the invention to provide a device having a much easier structure and allowing the inspection of the inner surface of a container. To this end the device according to the invention is characterized by a mirror having a generally frusto-conical shape and being disposed in both the path of the light beam directed from said light source to said standing inner surface and the path of the light beam directed from said standing inner surface (11) to said inspection means; the arrangement being such, that the light source, via said frusto-conical mirror, is adapted to illuminate the whole standing inner surface, and the inspection means, via said frusto-conical mirror, are adapted to view the whole standing inner surface; said light source, said inspection means, and said generally frusto-conical mirror being disposed distant from the hollow body. It should be noted that from EP-A-0 209 077 an apparatus is known that is adapted for detecting defects on a bottle mouth having a screw thread. In this prior art reference the use of a frusto-conical mirror is suggested. By making use of a generally frusto-conical mirror having a curved shape a still further effective enlargement can be achieved. In a specific embodyment the device is characterized in that that the light source 4 is substantially annular and is disposed around the inspection means (1). In this connection it should be noted that from the Patent Abstracts of Japan, vol. 11, no. 264, P-610, a defect inspection instrument for the mouth of a bottle is known, in which use is made of an annular light source disposed around a photoelectric conversion sensor. The invention will now be elucidated with reference to several embodiments. In the drawing: figure 1 shows a schematically represented first embodiment; figure 2 shows a schematic video image obtained with the disposition according to figure 1; figure 3 shows another embodiment. Figure 1 shows a video camera 1 and a light source 2 which gives off light by means of an optical conductor 3 via an end crown 4 of the light conductors. The light 5 coming from these light conductors 4 is radiated into a container 7 via a conical mirror 6. The light 8 coming from the lighted zone can be observed from approximately the same direction by the video camera 1. The drawn rays 5, 8 indicate one lighting and inspection zone only by way of example. Figure 2 shows a video image 9. The video camera 1 "sees" the bottom of the can directly, as well as the standing inner wall 11. The video camera 1 further inspects the inner wall 11 via the conical mirror 6. This image zone is designated in figure 2 by 11′. It will be apparent that the use of the conical mirror 6 achieves as it were an optical enlargement of the standing wall whereby the resolving power of the optical system is better utilized. This is to the benefit of the detection sensitivity. By making use of a curved mirror instead of the conical mirror 6 a still further effective enlargement can be achieved. Figure 3 shows a disposition wherein a light source 12 lights the inner surface 11 of the can 7 via a semi-transparent mirror 13. The light source 12 is placed in relation to the video camera 1 and the semi-transparent mirror 13 such that the optical centre point of the lens system of the camera 1 coincides with the effective location of the light source of the lamp 12.

Claims: A device for inspecting the inner surface (10, 11) of a hollow body (7) having a cylindrical standing wall (11) and a bottom (10), said device comprising: positioning means for placing said body (7) at a chosen position; a light source (2, 3, 4) placed relative to said positioning means such that it can illuminate said inner surface (10, 11); and inspection means (1), e.g. a video camera, placed relative to said positioning means such that it can view said inner surface (10, 11); whereby the direction of lighting and the direction of inspection of each portion of the said inner surface (10, 11) at least approximately coincide; characterized by a mirror (6) having a generally frusto-conical shape and being disposed in both the path of the light beam (5) directed from said light source (2, 3, 4) to said standing inner surface (11) and the path of the light beam (8) directed from said standing inner surface (11) to said inspection means (1); the arrangement being such, that the light source (2, 3, 4), via said frusto-conical mirror (6), is adapted to illuminate the whole standing inner surface (11), and the inspection means (1), via said frusto-conical mirror (6), are adapted to view the whole standing inner surface (11); said light source (2, 3, 4), said inspection means (1), and said generally frusto-conical mirror (6) being disposed distant from the hollow body (7). The device according to claim 1, characterized in that the generally frusto-conical mirror (6) has a curved shape. The device according to claim 1, characterized in that the light source 4 is substantially annular and is disposed around the inspection means (1). The device according to claim 1, characterized in that a semi-transparent mirror (13) is disposed such that the (virtual) image of the light source (12) substantially coincides with the inspection means (1).

Inventors: OBDEIJN MARCELLINES JOHANNES J, OBDEIJN, MARCELLINES JOHANNES JOZEF
Applicants: HEUFT SYSTEMTECHNIK GMBH
Application year: 1989
Main classification: G01N21
IPC codes: G01N21, G01B11