| 摘要 |
PURPOSE:To decrease tracking and focusing in offset, by providing a 4-split photodetector for light spot position deviation signal on the center of rotation of a swing arm. CONSTITUTION:The swing arm 10 is provided with a laser light source 1, coupling lens 2, triangular prism 3, polarizing prism 4, lambda/4 plate 4, stop-down lens 6, lens 7, cylindrical lens, and mirror 16 internally. Light from the laser light source 1 is reflected by a track 13 of an optical disk 12 and passes through the optical system in the swing arm 10 to reach the 4-split photodetector 9. The 4- split photodetector 9 generates a tracking and a focusing error signal, but the photodetector 9 is provided on the center of rotation of the swing arm independently, so even when the swing arm is rotated to cause a shift in light spot position on the optical disk 12, influence upon said two error signals is less. |
