Visual inspection is widely used in the tire manufacturing process and even more commonly relies on the skill of the operators tasked with checking for the absence of visible imperfections at the surface of the tires in order to ensure the compliance thereof.
However, with the advances in the computing power of computer-based means, tire manufacturers are developing automatic inspection means to assist the operators tasked with the visual inspection. To this end, it is possible to use an inspection device comprising lighting means and cameras which are positioned in such a way as to scan the exterior and interior zones of the lateral beads and of the tread of the tire that is to be inspected. The viewing field of each camera is angularly limited. In order to obtain complete images of the inside and of the outside of the tire, the tire has to be turned about its axis with respect to the lighting means and with respect to the cameras. The digital images obtained are then processed and compared against reference images in order to determine whether there might be any surface and appearance anomalies in the tire. For further details, reference may for example be made to patent applications EP-A2-1 959 227, EP-A1-2 023 078 and EP-A1-2 172 737.
In order to carry out such an inspection with a good degree of precision, use is generally made of an image acquisition device equipped with a laser lighting means that allows a line of light to be projected onto the tire and with a matrix camera capable of capturing the light reflected off the tire and which is oriented at a triangulation angle. The triangulation angle is the angle formed between the optical axis of the laser lighting means and the optical axis of the camera.
In order to be able to detect very small imperfections at the surface of the tire, the triangulation angle generally chosen is relatively large. As a result, the overall size of the image acquisition device is large.
Now, in order to be able to capture a complete image of at least half the interior surface of the tire in a single rotation thereof, it is necessary to install a plurality of image acquisition devices penetrating the interior space of the tire.
Given the overall size of each image acquisition device it may therefore be particularly tricky if not to say impossible to achieve this installation for certain tire sizes, for example for tires in the current size range for passenger vehicles.
The present invention seeks to overcome this disadvantage.