Defects detection for rough magnetic tiles surface based on light sectioning

Magnetic tile as a kind of product of mass production and wide application in electronic motors, and defects detection is a major issue in its production line. In this paper, a machine vision method based on black-stripe projection is presented to deal with this issue. Because of magnetic tile surface with black colors, rough structure and complex grinding textures, we abandon intensity imaging and resort to light sectioning methods which provides more reliable and abundant surface information. In order to suppress the speckle diffraction effect caused by laser light source, we used the light-emitting diode (LED) with incoherent characteristics. The black-stripe images were captured by a high-speed camera. A fast algorithm was developed to extract and compare both edges of the black-stripe, which could detect defects and eliminate the effects of vibrations. The experimental results show that the simple and fast processing method proposed in this paper can detect the structural defects such as micro pits and micro cracks.