Optical disc apparatus, focus position control method and recording medium

Abstract

An optical disc apparatus can highly accurately record a hologram representing information on or reproduce such a hologram from an optical disc. When recording information on an optical disc, the optical disc apparatus controls the position of an objective lens OLaccording to the outcome of detection of a red reflected light beam Lrso as to make the focus Fr thereof follow a target track and it also makes the focus Fbof a blue light beam Lbagree with a target mark position by the objective lens OLand also the focus Fbagree with the target mark position by controlling the position of another objective lens OLaccording to the outcome of detection of the blue light beam Lbby way of the objective lenses OLand OLso as to make the focus Fbof the blue light beam Lband the focus Fbof the blue light beam Lbagree with the target mark position and the blue light beam Lband the blue light beam Lbinterfere with each other. Thus, as a result, the optical disc apparatus can record a recording mark RM at the target mark position.