Patent ID: 6996043

Claim:
An optical head apparatus on an optical path of a light beam between an objective lens and an information recording medium, comprising: an immersion lens positioned at a floating height with respect to a surface of the information recording medium; a detector that measures a height of a foreign material on a surface of the information recording medium by detecting the intensity of a scattered light in proportion to a height of the foreign material on the information recording medium; a controller for outputting a control signal corresponding to the height of the foreign material if the height of the foreign material is higher than the floating height of the immersion lens; and a movement unit that moves the immersion lens to a position higher than the height of the foreign material, the movement unit moving the immersion lens by a distance corresponding to the control signal, wherein a predetermined time of a delay detection signal necessary for the movement unit to move to a predetermined height is set to a shorter time than a time in which the foreign material reaches the position of the movement unit after the detector detects the foreign material.