| 摘要 |
PURPOSE:To improve the tracking performance by arranging a prism so as to bend an optical axis at an angle not being a right angle thereby widening the tracking enable range. CONSTITUTION:A laser beam from a laser 1 passes through a half mirror 4, refracted at a prism 23 having a angle beta, the optical axis is bent by an angle alphabeing not a right angle, radiates a disk 10 to be split lights 30-1, 30-2 having an interval delta2. Then the reflected light is reflected in the mirror 4 via the prism 23 and received by spot light detection sections 9a, 9b having an interval delta. Through the constitution above, the interval ratio delta/delta2 is larger than the unity in response to the angles alpha, beta. As a result, the tracking range is widened and the tracking performance is improved. |
