We use ray-trace equations for uniaxial biréfringent materials to derive third-order estimates for aberrations that are produced in imaging through uniaxial plates and horizontal-vertical (HV) depolarizers. An HV depolarizer is a spatial pseudodepolarizer; it converts a uniform input polarization state into acontinuum of spatially varying polarization states in an output beam. An HV depolarizer consists of twobiréfringent wedges whose crystal axes are crossed at 90°. The interface between the wedges is inclined, which leads to a spatially varying retardance that provides the spatial pseudodepolarization. In HVdepolarizers, spherical aberration, astigmatism, and image doubling are the principal aberrations foron-axis objects. Only spherical aberration occurs in isotropic plates, while the presence of biréfringentwedges introduces astigmatism and image doubling. It is shown that image separation is proportional tothe magnitude of the retardance variation. Image separation is independent of the thickness, wedge angle, and refractive indices that are used to achieve this variation. A computer program is used to perform anexact biréfringent ray trace and produces spot diagrams that confirm the aberration estimates.
- Ray tracing
ASJC Scopus subject areas
- Atomic and Molecular Physics, and Optics