Method and device for determining geometric information relating to interfaces of an optical element

A measurement method, for determining an item of geometric information of an interface to be measured of an optical element with respect to a measurement axis, the optical element comprising at least two interfaces, the method being implemented by a measurement device having a reference axis and comprising interferometric measurement means with at least one optical sensor and at least one low-coherence light source, configured for directing a measurement beam along the measurement axis 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 for selectively detecting an interference signal resulting from interferences between the reflected measurement beam and a reference beam, the device further comprising positioning means and digital processing means,

• the method comprising the following steps:
• relative positioning, by the positioning means, of a coherence area of the light source at the level of the interface to be measured;
• at least a first step of measurement and a second step of measurement of the interface, by the interferometric measurement means, so as to produce one interference image per measurement step from respective interference signals;
• rotation of the optical element about the reference axis between the first measurement step and the second measurement step;
• and
• processing, by the digital processing means, of the one interference image per said measurement step, so as to obtain an item of information relating to the interface,
• wherein the processing step comprising a step of determining an item of decentering information of the interface and a step of obtaining an item of geometric information of the interface to be measured, wherein the same at least two interference images for one interface to be measured are used to obtain both the decentering information and the item of geometric information.