Product Description
This device is a flawless condition Special Optics Soleil-Babinet Compensator complete with an indexing graduated theta stage. Special Optics manufactures several different types of these compensators using both quartz and MgFl for the birefringent elements. They are also available with differing measuring ranges as well as two aperture diameters. This particular instrument is the smaller type, with a 10mm aperture. I am fairly certain that it is the model 8-400 with a maximum retardation of 900nm. When using white light between crossed polarizers it only appears to go through about 1.5 orders of colors to one side of the extinction position which is close to one end of the travel, but this was a fairly crude test. Unfortunately, there is no part marking on the instrument itself. It has been calibrated for a HeNe laser at 632.8nm.
The instrument is pin-mounted. The theta stage can be rotated 360 degrees graduated every degree. A really nice feature of the stage is that it may be clamped in an ‘extinction position’ for instance, and immediately indexed to any 45-degree position independent of the clamped position.
These compensators can be used to convert any type of polarized light form into any other form of polarization (linear to elliptical, circular, or vice versa). The active elements combined yield a wavefront deformation less than 1/10 wave. For accurate measurements it is important that the compensator be orthogonal to the source.
The size of the optical post on the unit is 13mm.
The instrument does include a very heavy-duty wood cabinet that appears to have been adapted for its stowage (I do not think it is the original, but it fits nicely, and is very secure).