| 摘要 |
PURPOSE:To correct astigmatism varied every semiconductor laser element by adjusting the position of an optical means which corrects the astigmatism of a light beam at the time of assembling and adjusting an optical head. CONSTITUTION:A laser beam 3 emitted from the semiconductor laser element 1 is passed through a collimator lens 2 after it is passed through a cylindrical lens as the optical means 51 which corrects the astigmatism of light. The lens 51 acts as the lens in the direction that the lens 51 has power (a curvature direction) and the converging and diverging state of the beam 3 after it is passed through the lens 51 is changed according to the position of the lens 51 with respect to the element 1. Thus, the astigmatic difference value of the laser beam can be optionally set. The laser beam whose astigmatism is eliminated is made incident on the elliptical correction surface 17 of a polarizing beam splitter 15 and the cross section thereof is corrected to be elliptical. The beam is focused on the recording surface of a recording medium 8 through the splitter 15, a lambda/4 plate 9 and an objective lens 7 and recorded or reproduced. |
