Description

The Fresnel rhomb is unique among retarders in giving a fractional-wave retardation nearly independent of wavelength, the variation due to change of index with wavelength being less than ±1% through the visible (450-700nm) and within ±4% throughout the range of transparency (350-2500nm). The variation with angle is also small (less than ±6% over ±5°) and spurious stress birefringence is reduced by use of a fine-annealed grade of glass. The single (quarter-wave) rhomb gives an output parallel to the input but laterally displaced. The double (half-wave) rhomb has input and output coaxial.