| 摘要 |
PURPOSE:To obtain a stable focus state, by blowing off the air through pads provided at the front and rear sides and on both sides of the reading position of a recording medium corresponding to an objective lens and keeping a fixed distance between the reading position and the objective lens. CONSTITUTION:Pairs of pads 18-21 which hold a disk 1 at its both sides are provided to a recording layer 1a of a disk 1 and at a part corresponding to an objective lens 10, i.e., at the front and back sides of the revolving direction centering on a reading position 17. The surface deflection of the layer 1a is suppressed by the air blown off through openings 18b-21b provided to the pads 18-21 respectively. Thus the surface of the layer 1a is always fixed at a prescribed position. Therefore a stable focus state is always kept after a focus control is once performed so as to obtain a fixed distance l between the lens 10 and the reading position. |
