| 摘要 |
PURPOSE:To easily, independently and stably obtain the control information for recording and reproducing by approximately concentrically providing guide grooves for tracking control of specific depths and disposing flat parts having no radial guide grooves across the plural guide grooves. CONSTITUTION:The guide grooves 2 for tracking control of the depth of 1/8 the wavelength of a light beam are approximately concentrically provided on a substrate material 1 and the flat parts 20 having no guide grooves are radially disposed at equal angular intervals. As a result, the signals corresponding to the disconnected points of the grooves 2 are obtainable from the output of a tracking detector. Then, tracking of control formation on disk rotation, reference for timing reproduction and reference for writing signals, etc., and information reading and writing are independently controlled at need and such control is usable for various kinds of control at need. |
