| 摘要 |
PURPOSE:To perform easy and accurate control of a holding barrel of an objective lens, by holding the holding barrel movable in both tracking and focusing directions while adsorbing or attracting magnetically the holding barrel to a static magnetic path and then performing the position control of the holding barrel by controlling the current of a control electromagnet. CONSTITUTION:An objective lens 12 is held by a holding barrel 13. An outer barrel 11 is made of a magnetic matter and the magnetic flux of a magnet 20 pierces through the barrel 13. The barrel 13 can move in both tracking and focusing directions by means of a bearing 19 containing a steel ball 17 and guide grooves 14 and 18. The barrel 13 is attracted to the bearing 19 by the magnetic force. An electromagnet 22 has four projected magnetic poles and controls the current supplied to each of coils 25a-25d to move the barrel 13. A magnetic fluid 26 is injected to a magnetic gap in order to increase the density of magnetic flux as well as to control the mobile part. |
