An aberration correcting mechanism includes a corrective optical glass for correcting a spherical aberration and a link mechanism for movably supporting the corrective optical glass. The corrective optical glass is a parallel, flat plate having the same refractive index as that of a cover glass of a...http://www.google.com.au/patents/US5930224?utm_source=gb-gplus-sharePatent US5930224 - Information recording/reproduction apparatus
