| 摘要 |
PURPOSE:To specify a specific interval as a home position for a pickup and to position a linear scale by forming signal grooves with different signal levels in every fixed interval on a position other than a recording area of a master plate. CONSTITUTION:Signal grooves 6a-6c for a group or bits making a pair having three or more different signal levels are formed in each interval 5 so that the shapes of the grooves are different in each interval 5. At the time of laser cutting of the master plate 1, respective grooves 6a-6c change an exposing position based upon a lens and a resist plate or the quantity of light to execute exposure formation. Thereby, the signal groove 6a is formed as a reference groove shape and the signal grooves 6b, 6c are formed as groove shapes having a condition capable of outputting upper and lower levels from the tolerance of a signal outputted from the signal groove 6a. Since a specified address is jumped back and a signal can be obtained from a specified interval 5, the signal is picked up as a home position to position the linear scale. |
