Abstract: This invention provides a multipass Solc filter which utilizes liquid crystal variable retarders to provide high resolution and tunability. The Solc polarization-interference effects are used synergistically with the Fabry-Perot cavity resonances. The cavity comprises a central retarder, two quarter wave plates, and an optional isotropic spacer. The central retarder or the isotropic spacer can include liquid crystal cells to provide tuning of the Solc envelope or the cavity resonances respectively. In one embodiment the variable retarder is a three element quarter-half-quarter device with a liquid crystal electro-optically rotatable half-wave plate. Reflection mode configurations are introduced wherein, because of the bilateral symmetry of the Solc filter, it is possible to use only half of the intracavity elements. Criteria for designing filter parameters to meet resolution, out-of-band discrimination, and tuning range requirements are provided.