Project name Ellipsometer
Client / customer VSL - Dutch Metrology Institute
Partners -
Description VSL develops a compact scanning ellipsometer for the characterisation of large (typically 1 m2), flat samples. The work is part of the Thin Films project of the European Metrology Research Programme (EMRP).

Although ellipsometers are readily available (e.g. J.A. Woollam, Gaertner, Horiba), these cannot handle the required large samples. Furthermore, their high weight and bulky design make these instruments unsuitable for use in a scanning ellipsometer set up, e.g. move the ellipsometer relative to a stationary sample.
Therefore VSL asked Entechna to help with the design of a compact, lightweight ellipsometer which can be installed on a large-stroke coordinate measuring machine (CMM). Entechna made a design based on the VSL-provided optical layout.

Ellipsometry measures the change in polarization state of light reflected from, or transmitted through, the surface of the sample under study. During measurement, the input beam's angle of incidence changes from nearly perpendicular to nearly grazing incidence.

In a concept study, Entechna developed a simple and elegant alternative (figure 1) to the conventional ellipsometer layout. In this concept, the input optics and output optics synchronously rotate around mutually perpendicular axes so the incident and reflected beams are symmetrical around the surface normal. High resolution optical encoders measure the rotations.

Summary (PDF) -

1: concept 2: detailed design 3: detailed design

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