| 摘要 |
PURPOSE:To eliminate an unstable mobile phenomenon caused by the high speed leading of an initial driving circuit of an objective lens, and a mechanical friction generated until reaching the control area of a focus servo-mechanism, by giving a minute vibration to the objective lens. CONSTITUTION:From a storage element 32 storing a control voltage data obtained by adding the second clock signal having an amplitude and a pulse width determined in advance, to the first DC signal having the number of steps determined in advance, its data is outputted, by receiving a leading-in start signal 21, and when it is converted to an analog control voltage through a D/A converter 33, a control voltage whose leading time is short is obtained. By only this variation, the moving extent of an objective lens cannot be forecast due to the friction of a supporting mechanism, etc., of the objective lens, therefore, by superposing a high frequency signal for giving a minute vibration to the objective lens, onto said control voltage, the influence of the friction can be obviated virtually. Accordingly, focus leading-in which can shorten the driving time can be executed. |
