| 摘要 |
PURPOSE:To accurately detect the edge position of a pit by eliminating a DC component in a reproduced signal when an objective lens is moved in the direction of tracking. CONSTITUTION:A lens position senser 1 irradiates a reflection plate on the side part of a lens barrel of the objective lens 121 with an LED, and a phototransistor receives it. The lens 121 is moved in the tracking direction of the disk, and an output signal according to the moving amt. is obtained and sent to an addition and subtraction circuit (not shown in figure). By a differential amplifier 119, a signal from a detection piece of a bisected photodetector 124 is differential-detected and reproduced. A positive or negative DC component is added to the reproduced signal according to a shift direction when the objective lens 121 is shifted in the radial direction of the disk 105, and the DC component is varied in response to the shift at. The obtained reproduced signal is sent to the addition and subtracting circuit and added/subtracted so as to cancel the DC component, and is corrected so as to have no DC component always. Then, even when the objective lens is shifted, the position of the area end edge is detected accurately and the information is reproduced accurately. |
