Method for Aligning the Axes of a Birefringent Bifocal Lens System
Original Publication Date: 1985-Apr-01
Included in the Prior Art Database: 2005-Feb-18
A method is described for aligning the optical axes of a birefringent bifocal lens system using plane light wave illumination and a laser interferometer to observe interference rings. A birefringent element objective may be used, for example, in an X-ray lithography manual alignment system. Such a bifocal element objective was originally proposed by A. White[*]. The system consists of two relatively weak (large radii) quartz lenses, one convergent (plano-convex) and one divergent (plano- concave). The two lenses are cemented together with the ordinary axis in one lens parallel to the extraordinary axis in the other lens (Fig. 1). In operation, the cemented lenses are placed behind the regular objective of an alignment microscope.