Method for detecting a defect on a surface by multidirectional lighting and associated device

A device for detecting a defect on a surface, the detection device including:

• an optical device having an optical axis, the optical device being configured to acquire an image of the surface along a given optical direction;
• a lighting device having several different lighting direction;
• and
• an electronic calculating device, the electronic calculating device being configured to:
• acquire a plurality of images of the surface via the optical device, each image being acquired along the given optical direction with different lighting directions or different combinations of lighting directions for each image,
• for each point of the surface, calculate, from acquired images, a plurality of parameters, the parameters including coefficients of an equation characterizing the response of the point of the surface as a function of the lighting direction and an observation direction;
• wherein, for each point of the surface, the calculation of the parameters includes:
• defining a quantity evolving as a function of the acquired images;
• choosing a model of the surface depending on the lighting direction(s) and/or the observation direction for the evolution of the quantity, the model including the coefficients, and calculating coefficients by regression of the evolution of the quantity;
• and
• deduce from the calculated parameters whether the surface has a defect at the point.