| 摘要 |
PURPOSE:To reduce a track error, and to make tracking accurate by forming a title diode so that the position of the illuminant point of a central beam in a plane perpendicular to an emitted light is distant from a straight line connecting the positions of the illuminant points at both ends by a prescribed distance, by using a prescribed calculation expression. CONSTITUTION:Respective intervals between a central spot 52' and the spots 51 and 53 at both ends on the recording medium 5 of a radius R are assumed to be H respectively, and the movement DELTAx of a light beam for changing the distance of the central spot 52' to the straight line, connecting the spots 51 and 53, by the distance DELTAy, is given by DELTAx=f.DELTAy/F when the focal lengths of collimate lens 2 and an objective lens 4 are assumed to be f, F respectively, and the value of the distance DELTAy comes to be y=H<2>/2.R. From these two expressions, the distance DELTAx between the illuminant point P2 and the straight line, connecting the illuminant points P1,P3 of the two beams at the both ends, in the plane perpendicular to the emitted light, comes to be DELTAx=f.H<2>/2.R.F, and the value of DELTAx is obtained by using this calculation expression, and respec tive laser diode chips 11-13 are positioned in a package 14. |
