| 摘要 |
PURPOSE:To accurately execute tracking detection by setting up a distance from the incident light deflecting point of a deflecting member up to the center of a moving lens about twice as long as the focal distance of an objective lens to an optical disk. CONSTITUTION:When the distance from the incident light axis deflecting point P of the deflecting prism 20 up to the center of the objective lens 19 is l and the focal distance of the objective lens 19 to the optical disk 1 is (f), l=2f is set up. When a carriage 18 is rotated around the X axis rectangular to its seaking direction S only by angle theta, an offset value DELTAx between the incident light axis 23 to the prism 20 and reflected light axis 24 from the prism 20 is found out by the shown equation I. When l=2f is substituted for the equation I, DELTAx=0 is formed, so that even when the carriage 18 is inclined by the angle theta, the incident light axis 23 coincides with the reflected light axis 24 and accurate tracking detection can be attained. |
