Method for permanent visible marking of an optical article and marked optical article

A method for marking an optical article (1, 20), said method including at least one step of use of a marking machine on the optical article (1, 20):

• The marking machine being a marking machine that marks with an electromagnetic beam (23), said marking machine including an electromagnetic source configured to emit a beam having a set radiation wavelength called the marking wavelength;
• The optical article being an optical article (1, 20) including a substrate (6, 21) having a main face coated with an interference coating (2,3,4,5;
• 14,15,16,17,18,19), said interference coating comprising at least two superposed layers called the interior layer (4, 15) and the exterior layer (2, 14), the interior layer being located between the substrate and the exterior layer, the interference coating being such that it has a reflection coefficient Re in the visible domain (380-780 nm);
• The use comprising irradiating at least the interior layer (4, 15) in a given spot called the marking spot (25, P), by means of the laser beam at the marking wavelength, so as to ablate, in the marking spot, the interior layer, over at least one portion of its thickness, and any layer located between the electromagnetic source and the interior layer;
• and being such that the ablated zone has a reflection coefficient Rm in the visible domain (380-780 nm), Rm being different from Re by at least 1%;
• The interior layer absorbing the marking wavelength more greatly than any layer located between the electromagnetic source and the interior layer.