Patent ID: 8040510

Claim:
An apparatus for optically treating or measuring a target through a birefringent layer having an optic axis, comprising: a light source adapted to generate a treatment or measurement beam having an incidence direction and a polarization characteristic, and a monitor beam; a monitoring apparatus for monitoring an orientation of the optic axis or effects that indicate the orientation; and an alignment apparatus for adjusting the relative orientation of the optic axis and at least one of the incidence direction or the polarization characteristic based on the monitored data; where the monitor beam forms at least a first spot and a second spot on the target with respective intensities I 1 and I 2 , widths W 1 and W 2 , and a distance d between centers of the two spots, where I 1 is greater than I 2 , and W 1 is greater than W 2 ; the monitor beam enters the birefringent layer at an incident locus; the birefringent layer can split beams with some combinations of incidence direction and polarization characteristic into ordinary and extraordinary components propagating at different angles; and an optimal adjustment of the alignment apparatus, based on at least one of I 1 and I 2 , W 1 or d, creates an acceptably resolved pattern at the target.