Optical disks are read out by focusing a beam of high numerical aperture (NA) through the substrate. Deviations of the thickness from the nominal value result in spherical aberration; tilting the substrate results in coma. Exact analytical expressions for the rms aberration per micrometer thickness mismatch (for spherical aberration) and per degree tilt (for coma) are derived. The paraxial estimates for these sensitivities proportional to NA4 (spherical aberration) and NA3 (coma) underestimate the exact values by a factor of ~2 for the value NA = 0.85, corresponding to the new Blu-ray disk format. Expansion of the aberration function in Zernike aberrations shows that the exact aberration functions are well described by the lowest-order Zernike spherical aberration (A40) and coma (A31) term for all but the very highest NA values.
© 2005 Optical Society of America
Original Manuscript: June 9, 2004
Revised Manuscript: September 14, 2004
Manuscript Accepted: September 18, 2004
Published: February 20, 2005
Sjoerd Stallinga, "Compact description of substrate-related aberrations in high numerical-aperture optical disk readout," Appl. Opt. 44, 849-858 (2005)