| 摘要 |
PURPOSE:To facilitate an assembly and an adjustment by branching an incident light beam, branching it further to light beams to be approximately parallel mutually, answering the light beams and adjusting the position in the optical axis direction of a focusing means to a recording medium and the position in a plane surface vertical to the optical axis. CONSTITUTION:A laser beam L from a semiconductor laser 11 passes or is reflected at a half prism 14, the reflected laser beam L is transmitted through a lens 17, it is made incident on a beam splitter 30, and a light beam La further reflected here is made into a tracking error signal through a detector 21 by a comparing circuit 42. A light beam Lb transmitted through the joined surface of the beam splitter 30 is made incident on a light refracting bodies 18 and 19, branched into two parallel light beams L1 and L2 and made into a focusing error signal through a photodetector 20 by a comparing circuit 41. The electric signals are supplied from a driving circuit 44 to a voice coil 8, and an objective 16 is driven. Thus, the interval of the light beam is maintained approximately fixed without being influenced by the dislocation of the optical axis of each optical part, and the assembly and adjustment are made easy. |
