Apparatus and method for optical inspection of objects, in particular metal lids

An apparatus for optical inspection of objects, in particular metal lids, comprising:

• a camera oriented according to a vertical viewing axis to see the object to be inspected positioned in an inspection station and to capture an image of the object;
• a first illuminator configured to emit rays of light at a first frequency, and being inclined at a first inclination angle to the viewing axis to subject the object in the inspection station to grazing light at the first frequency;
• a second illuminator configured to emit rays of light at a second frequency different from the first frequency, and being inclined at a second inclination angle to the viewing axis, smaller than the first inclination angle, to subject the object in the inspection station to top-down light at the second frequency;
• a third illuminator configured to emit rays of light at a third frequency, different from the first and second frequencies;
• a processor connected to the camera and programmed to process the captured image and generate from it a first, a second and a third filtered image corresponding to the illumination contributions of the first, second and third illuminators, respectively and separately,
• wherein the third illuminator is mounted on a three-dimensional surface positioned around the inspection station and around an optical path defined by the camera, so that the light rays emitted by the third illuminator are inclined at a plurality of different inclination angles to subject the object in the inspection station to diffused light at the third frequency,
• the third illuminator including a plurality of lighting elements, wherein:
• a first lighting element of the plurality of lighting elements of the third illuminator is inclined, with respect to the viewing axis, according to a third inclination angle, the third inclination angle being smaller than the first inclination angle of the first illuminator;
• a second lighting element of the plurality of lighting elements of the third illuminator is inclined, with respect to the viewing axis, according to the second inclination angle of the second illuminator;
• whereby both the second illuminator and the second lighting element of the plurality of lighting elements of the third illuminator are inclined at the second inclination angle, to subject the object in the inspection station to top-down light.