| 摘要 |
PURPOSE:To obtain the form of an optimum erasure light spot by giving a specific phase difference to the specific part of a light beam wave front. CONSTITUTION:Electrooptic elements 35, 36, 37 of a phase converting means 21 have the same thickness (the thickness is in the depth direction in figure), and they are insulated respectively by an insulation plate 39 and connected. The polarized direction of the incident light beam is directed to the arrow, that is, the same as the direction of double refraction and when applying a voltage to the electrooptic element 36, a phase difference is given to only the light beam passing through the said part. Various light spots are formed by the value and position of the phase difference given to the light beam and formed suitable for erasure while being scattered in the track direction. Thus, the recording/reproducing light spot and the erasure light spot are formed from one semiconductor laser and no positional-shift is caused. |
