| 摘要 |
PURPOSE:To reduce the number of components and to make adjusting work unnecessary, by providing a DC component detecting means to detect the DC component of a tracking error signal, and a travel quantity detecting means to detect the amount of travel of an objective lens based on a detected DC component. CONSTITUTION:The position of the objective lens M1 of an optical pickup M4 which outputs the tracking error signal TE by a push-pull method is detected from the output of an optical detector M3 to which a beam of light via an optical disk M2 is introduced. In other words, the DC component and an AC component are included in the tracking error signal TE, and the DC component shows the travel quantity from the neutral point of the objective lens M1. Then, the DC component is detected by the DC component detecting means 5, and the position of the objective lens M1 is detected by the amount of travel detecting means M6 based on the DC component. In such a way, no additional light source or detector to detect the position of the objective lens is required, thereby, it is possible to miniaturize the constitution of a device, and to make the device light in weight.
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