| 摘要 |
PURPOSE:To make marking pitch fine and to take a measurement with high accuracy by marking many pits in an optical disk in a peripheral direction, providing the disk to a fixed base or body of rotation and scanning laser light, and reading the pitch and obtaining pulses. CONSTITUTION:The optical disk 6 is constituted by using a transparent plastic disk as its base material, forming two guide tracks 8 concentrically on its one surface, and marking pits 9 of the same length at constant division angles along a circular center line between the tracks and then vapor-depositing an Al reflecting film on the surface. Then, laser light from the laser diode of an optical pickup unit 12 for horizontal graduations is projected on the array line of pits 9. When the unit 12 swivels and moves, pits 9 are scanned with the laser beam and the photodiode of the unit 12 generates an electric signal corresponding to the scanned pits 9. This electric signal is detected 23 as pulses and then counted 25 after necessary signal processing 24, and the counted value is displayed 26 digitally as horizontal graduations. In this case, the angle of rotation of the disk 6 is read in 10sec units.
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