Method and device for measuring interfaces of an optical element

A measurement method, for measuring an item of geometric information of an interface to be measured of an optical element comprising at least two interfaces, the method being implemented by a measurement device comprising interferometric measurement means with at least one optical sensor and a low-coherence source, configured to direct a measurement beam towards the optical element so as to pass through at least one of the at least two interfaces, and to be reflected by the interface to be measured and generate a reflected measurement beam, and to selectively detect an interference signal resulting from interferences between the reflected measurement beam and a reference beam, the device also comprising positioning means and digital processing means,

• said method comprising the following steps:
• relative positioning, by the positioning means, of a coherence area of the interferometric measurement means at an interface to be measured;
• measuring the interface by the interferometric measurement means, so as to produce a plurality of interference signals corresponding to a plurality of measurement points on the interface;
• and
• processing interference signals by the digital processing means, the processing comprising the following steps:
• constructing a mathematical interface based on at least one sub-set of interference signals for the interface;
• and
• determining, based on the mathematical interface and an expected shape of at least one first section of the interface, an item of geometric information of the interface to be measured, the step of determining the geometric information being performed by the following steps:
• deducing parameters of a model or of an analytical formulation of the first section of the interface;
• and
• modelling the shape of a second section of the interface to be measured, based on the parameters deduced, the second section of the interface being equal to or different from the first section of the interface.