| 摘要 |
PURPOSE:To make an optical head for magneto-optical recording and reproducing smaller in size and lower in cost by changing the polarization beam splitter used for the optical head from a bonded rectangular prism type to a plate type using parallel plane glass plates. CONSTITUTION:A plate type polarization beam splitter 9 with a polarizing film 10 on one of its parallel plane glass plates is provided between a convergent lens 8 and photodetectors 11 and 12, with the splitter 9 being inclined by 45 deg.. Therefore, the light beam made incident to this splitter 9 is separated into P-polarizing components and S-polarizing components. The transmitted light beam of the P-polarizing components produces astigmatism and focus error signals are detected by the photodetector 11. On the other hand, tracking error signals are detected from the reflected light beam of the S-polarizing components by means of the photodetector 12. Therefore, a cylindrical lens which causes astigmatism to be produced becomes unnecessary and only one convergent lens can be used for both focus error detection and tracking error detection. Thus the number of parts used in this optical head can be reduced an the optical head can be made smaller in size and lighter in weight. |
