| 摘要 |
<P>PROBLEM TO BE SOLVED: To provide an optical recording and reproducing device which corrects spherical aberration quickly even when there is thickness deviation in a cover layer of an optical recording medium of a high recording density. <P>SOLUTION: The device consists of an objective lens 22 for focusing a laser beam emitted through an expander means 16 on the optical recording medium D; a driving means 34 which obtains the amplitude ratio of the long/short periods of a reproduced signal of the optical recording medium D based on a photoelectric-converted signal of the received reflection light from the optical recording medium D and moves the expander means 16 in the direction of the optical axis of the laser beam based on the result of this, and an aberration control means 32 for outputting an instruction signal where a difference value becomes 0 to the driving means 34 based on a correlation between the difference value of the amplitude ratio in front and rear of the position of the objective lens 22 where the laser beam is focused at a position to which the expander means 16 is moved in the direction of the optical axis of the laser beam by the driving means 34 and a position to which the expander 16 is moved. <P>COPYRIGHT: (C)2006,JPO&NCIPI |
