Optical tolerances of an actively tilted high-numerical-aperture two-lens objective for optical recording

Analytical expressions for the primary wave-front aberrations of an actively tilted two-lens objective are derived, and expressions for the higher-order wave-front aberrations for disk tilt of this lens system are presented. This analysis is important because the two-lens objective opens the way to achieving higher-numerical-aperture systems for optical recording with acceptable tolerances that cannot be achieved with a single-lens objective. To test whether the conclusions drawn from the analytically derived results remain valid for high numerical apertures, we compare the results with those obtained by ray tracing: It is shown not only that the two-lens system is tolerant of disk-thickness variations and decentering of the lenses but that it can also be made tolerant of disk tilt when the lens facing the disk is actively tilted. (C) 1998 Optical Society of America.