Patent ID: 6081488
Filing Date: 2000-06-27
Classification: G11B

Abstract:
An optical head capable of recording or reproducing optical information onto or from optical disc media having differing substrate thicknesses from each other by collecting light that is emitted from a laser light source, via an intervening objective lens, onto an optical disc as a minutely small spot, said objective lens being designed to accommodate the substrate thickness of a first optical disc, when said laser light source is at a specific prescribed first position on an optical axis with respect to said objective lens, said objective lens, when used with a second optical disc of a different thickness than the thickness of the first optical disc, having a design which will give minimum aberration when said objective lens is placed in a second position on said optical axis, and a locator for positioning said light source at a specific prescribed actual or virtual third position between said first and second positions on said optical axis, said third position being a position at which not only is the wavefront aberration smaller than at said first position with respect to said second optical disc, but also there is not a significant reduction in the amount of allowed lateral skew compared with that at said first position.