New Linnik interferometer objective

Sensofar is pleased to announce the availability of a Linnik inteferometer objective as an optional module. A Linnik objective is designed to produce interference images of surfaces located deep within a transparent material or that are otherwise difficult to access. The opto-mechanical design of a Linnik objective comprises two identical objectives – one is focused on a reference surface and the other on the surface under inspection.

The combination of two bright-field objectives opens a handful of different possibilities. It can use super long working distance (SLWD) objectives, high numerical aperture, water immersion, or any pair of objectives that have a specification not available with conventionalintereferometers. The pair of objectives can be two 50x SLWDs for measuring PSI tilted surfaces, such as silicon wafers, at 45 degree without colliding with the objective. Alternatively, a pair of 20x EPI can be used to image protein crystals contained in water and that are covered with glass protection.

Despite its benefits, a Linnik objective is difficult to use and requires alignment expertise. It is normal to use a long coherence light source such a green or red LED with an interference filter.