Method and device for detecting and classifying a not-known object by a device having a two-dimensional field of view. The method includes a learning step, a detecting step and an inspection step. The learning step includes positioning a first known object in a field of view of the device and then positioning a second known object in the field of view of the device, to obtain images of the first and second known objects. Distinctive characteristics and common characteristics of the objects are identified and used to obtain an equality descriptor relative to common elements of the first and second known objects and a difference descriptor allowing association of the first and second known objects to two distinct classes. The device is then used to detect a third, not-known object. The equality descriptor and the difference descriptor are then used in an inspection step to classify the third not-known object.