| 摘要 |
PURPOSE:To correct the fall of the optical system of an optical system caused on a plane which is formed by the rotational center of an arm member and the optical axis of the optical system, by rotating the arm member at a proper angle to give displacement to the optical system. CONSTITUTION:It is assumed that an optical axis 115 of an objective lens 101 set in a lens holder 102 is fallen at an angle theta within a rotary plane of the lens 101 while no current flows to a focusing coil 109. An arm 103 is turned at an angle theta by the electromagnetic focus produced by supplying a fixed current for correction to the coil 109. Thus the lens 101 is displaced for correction of fall of the axis 115. Based on this state, the lens 101 is moved toward the axis 115 for focusing. In such a way, the fall of the axis 115 can be corrected within the rotary plane of the lens 101 by supplying a fixed current to the coil 109 in response to the fall angle.
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