| 摘要 |
PURPOSE:To eliminate the need of excess optical power in the case of erasing without lowering the resolution of an information bit at the time of reproduction even though a light spot has astigmatism by making the light spot on a recording medium an elliptic spot respectively having a major axis or a minor axis in the track direction at the time of erasing and reproducing a record. CONSTITUTION:A light beam projected from a light source 1 passes through a collimator lens 2, is circularly shaped by a shaping prism 7 in terms of a beam cross-sectional shape, passes through a beam spliter 3, is bent by a deflecting prism 4 in terms of an optical path, and forms the light spot on the surface of the recording medium through an objective lens 5. The reflected light reversely advances so as to be reflected by the beam spliter, and is made incident on a detecting optical system, so that an information signal, a track error signal, a focusing signal, and a focusing error, signal, etc., can be obtained. As to the light spot having the astigmatism; the spot on the medium 6 is controlled to become the elliptic spot having the major axis or the minor axis in the track direction in the case of erasing or reproducing the information. Thus, the excess light is not required to irradiate an adjacent track in the case of erasing and the resolution of the information bit is improved in the case of reproducing. |
