| 摘要 |
PURPOSE:To utilize sufficiently energy for erasure at recording and to save energy of a device by forming integrally light beams for recording and erasing. CONSTITUTION:A beam out of a laser beam source 201 goes to a parallel beam by a lens 202, passes through a deflecting prism 203 as it is and goes to a circular deflected light beam by a 1/4 wavelength plate 204. Said beam condenses on a spot 301 by an objective lens 205, and gives a high output energy to a recording medium 101. The beam reflected by said medium 101 is converted into a straight line polarized light by the 1/4 wavelength plate 204, and reflected by about 100% by the polarization prism 203. The reflected beam is condensed by a lens 209, and its light amount is detected by a photodetector 210 and used for detecting the presence or absence of information, auto focusing and tracking. on the other hand, a beam for erasing is emitted from a laser beam source 206, converted into a parallel beam by a collimate lens 207, goes to an elliptical beam by two cylindrical lenses 220 and 221 and condenses at a spot 302 on the recording medium. |
