Method for inspecting for surface defects on a cast part made of single-crystal metal and system for implementing same

A method for inspecting a surface condition of a single-crystal metal foundry piece, the surface of the piece including possible defects resulting from an inhomogeneous orientation of at least one crystal lattice of the single-crystal metal, said method including:

• acquiring, by an image acquisition device, a series of images of the foundry piece lit by a polarised, collimated lighting device, and then
• analysing the series of images by an image processing device, said analysing including the following operations:
• determining, for each pixel of the image acquisition device, an intensity vector corresponding to an intensity variation of the same pixel in each image in the series of images,
• determining an average intensity of all the pixels of each image in the series of images and extracting a law of general intensity variation for the series of images,
• determining a law of individual intensity variation, specific to each crystal lattice, and
• determining the pixels belonging to a same crystal lattice,
• each image in the series of images being made for a different polarisation angle, which is modified by rotating an axis of polarisation of the image acquisition device, the polarisation angle being the angle between an axis of polarisation of a first polariser that is part of the lighting device and an axis of polarisation of a second polariser that is part of the image acquisition device.