| 摘要 |
PURPOSE:To compensate deviation of a focus controlling system due to fluctuations of temperature, etc., even if it occurs, and to perform main recording by correcting the focus controlling system to an optimum focus state, and performing focus control. CONSTITUTION:Beams are emitted from a light source 7 for recording and a light source 12 for reproduction, and an 8MHz signal for optimum focus determination is supplied to an optical modulator 8 for a specified time. A beam modulated by said signal is projected as a recording beam upon a recording medium 1. A program for focus correction is read out of the 1st memory 31 of a control circuit 29 and the focus of the recording beam 2 is varied with time. A focus controlling circuit 35 includes an error amplifier 38 and a driving amplifier 39 which generate a voltage corresponding to the potential difference between input terminals A and B to control a moving coil 40 coupled with a condenser lens 10. Consequently, even if a focus controlling system has deviation owing to fluctuations of temperature, etc., the deviation is compensated to perform main recording. |
