| 摘要 |
PURPOSE:To achieve accurate reference position detection with compact constitution by providing a gear for magnetic head movement and a gear for control, which faces said gear and has a prescribed period, with through holes which coincide with each other at a reference position, and then providing a light emitting device and a photodetecting sensor with the through-holes in-between. CONSTITUTION:A gear 7 for head movement fixed to a rotating shaft 6 having screw thread 5 conforming to the screw hole 4 of a magnetic head supporting member is rotated by a motor 8 through a gear 10 to move a magnetic head 1 in the width direction of a magnetic tape 8. A gear 17 for control is rotated on a rotating shaft 12 through a gear 11. When the magnetic head 1 is at a refere position, light from a light emitting device 14 is made incident to a photo-detecting sensor 15 through the through-holes of gears 16 and 17, thus detecting the reference position accurately. The relation between the rotational period of the gear 16 and that of the gear 17 is so set that the through-holes 16 and 17 are aligned to each other only at the reference position in the moving section of the head 1. The structure is therefore made compact. |
