Optical record medium judging method and apparatus and focus servo

Abstract

The distances from external surfaces to information record surfaces of the optical record mediums of various types are different from each other. An optical record medium judging method of judging the types of the optical record mediums is provided with the steps of: irradiating an information record surface of an optical record medium to be reproduced with a plurality of light beams to be focused on different positions on one optical axis; moving, so as to change a relative distance parallel to said one optical axis between an objective lens for prescribing focal points of the plurality of light beams respectively and the information record surface, the objective lens; receiving a plurality of reflection lights of the plurality of light beams reflected from the information record surface respectively, associated with a change of the relative distance; generating a plurality of focus error signals on the basis of the plurality of received reflection lights respectively; and judging a type of the optical record medium by comparing levels of the generated focus error signals respectively with a predetermined standard level.