A Soleil-Babinet compensator can be regarded as a retarder with variable path difference. It can be used for the determination of polarization states as well for the realization of arbitrary values of retardation.

The compensators are comprising a movable long wedge as well as a short wedge and compensation plate which are mounted with fixed position. The crystal axes of the compensator plate is aligned at 90° with respect to the axes of the wedges. This allows to achieve zero order retardation values. The sum of the center thickness of the wedges equals the thickness of the compensator plate. Therefore, the path difference is zero in the center position and the compensator can be set to retardation value of both signs. The path difference depends linearly on the displacement of the wedge. The wedge position can adjusted and determined precisely by means of a micrometer screw.

We offer several models made either from quartz crystal or from MgF ₂ an with different wedge angles. Small wedge angles grant a higher resolution of the path difference. However, for most applications the wedge angle has to large enough to obtain an adjustment range of at least ±λ/2 at the operation wavelength λ. The conditions determine the recommended spectral range.

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