Apparatus for detecting defects of elements to be subjected to examination, particularly metallic lids , comprising lighting means for lighting an element to be subjected to examination, said lighting means emit radiation beams according two or more frequencies (f 1 , f 2 , f 3 ) included within a range set beforehand and comprise a plurality of light emitting diodes (LED) for emission of said radiation beams, an image acquisition unit for acquisition of images, such as a camera or the like, able to detect image of said element to be subjected to examination lightened by said lighting means , a unit for processing images acquired by said image acquisition unit , suitable to detect said defects, each one of said radiation beams lighting said element to be subjected to examination according to an optical path, individuating an incidence angle (α) with respect to the surface of said element to be subjected to examination included between a grazing minimum incidence angle and a scattering maximum incidence angle, said lighting means comprise a diffuser , having a substantially hemispherical shape, with its concavity faced downward, provided at the top with a hole, through which said image acquisition unit detects image of said element to be subjected to examination, and said light emitting diodes of said lighting means are grouped in a first, a second and a third light emitting diodes assembly , said first light emitting diodes assembly is installed according to a ring arrangement outside said diffuser , so as to grazing lighten said element to be subjected to examination, and it is suitable to emit at a first minimum frequency (f 1 ) within the red field, said second light emitting diodes assembly is an installation of light emitting diodes according to a ring arrangement outside said diffuser , so as to lighten said element to be subjected to grazing scattering examination, and it is suitable to emit at a second intermediate frequency (f 3 ) within the green field and said third light emitting diodes assembly comprises a first light emitting diodes group , wherein the light emitting diodes are installed according to a ring arrangement above said diffuser , and a second light emitting diode group (35"), which is arranged vertically above said diffuser , so as to lighten said element to be subjected to scattering examination and it is suitable to emit at a third intermediate frequency (f 3 ) within the blue field, characterized in that said lighting means further comprise a beam splitter mirror , provided above said diffuser reflecting the radiation beam emitted by said second light emitting diode group (35") on said element to be subjected to examination and permitting detection of an image of said element to be subjected to examination by said image acquisition unit , wherein the lighting means are provided so that incidence angle (α), realized by the optical path of each one of said radiation beams emitted by lighting means with respect to a horizontal plane surface of said lid to be subjected to examination, is directly proportional with respect to the relevant emission frequency (f 1 , f 2 , f 3 ), whereby the first light emitting diodes assembly emits in the red field according to a minimum angle, with respect to a horizontal plane surface of said lid to be subjected to examination, to generate grazing illumination; the second light emitting diodes assembly emits in the green field according to an angle larger than that of the first assembly; the third light emitting diodes assembly emits in the blue field according to an angle larger than that of the second assembly, at about 90°, with a radiation beam directed substantially perpendicular on the lid . <EOS>