| 摘要 |
PURPOSE:To enhance the reliability of a detected push-pull signal and to obtain address information high in reliability. CONSTITUTION:A light beam from a semiconductor laser is divided into three beams by means of a grating, a disk is irradiated with the beams, the reflected beams are separated by a beam splitter 8, further separated by a Wollaston prism 9 complied with the polarization component and made incident on a second photodetector 13 through a convex cylindrical mirror 12. The convex cylindrical mirror 12 widens the reflected beam in the direction nearly orthogonal to the dividing line of the divided photodetector for detecting the push-pull signal of the second photodetector 13, forms it to be an elliptic shape and makes it incident on the second photodetector 13. Consequently, the allowable width of positional error of the divided photodetector for detecting the push-pull signal of the second photodetector 13 is widened and the adjustment is easily performed. |
