| 摘要 |
PURPOSE:To form a spot of an elliptical shape having a sufficient large ellipticity on a recording film of an information storage medium, by varying a proceeding state of a light beam from a light source by a beam state converting member provided in an optical path of the light beam generated from the light source for generating a divergent light. CONSTITUTION:In a beam state converting member 611, its base material 81 is constituted locally of a cylindrical Fresnel lens surface 80 of an aggregation of stripe-shaped planes of a narrow width, and each plane is placed at an angle inclined to each other against each adjacent plane, and also, each stripe plane has an inclination, therefore, at the time of passing through said plane, an erasing laser light Lb generaged from an erasing laser array 61b of a semiconductor laser array (light source) 61 is refracted, and goes into each different direction. Therefore, when the light beam is condensed by an objective lens 18, it is condensed to spots which are shifted slightly from each other on an information storage medium 1, and as a total light by its superposition, an elliptical beam spot is formed. |
