DRIVING METHOD FOR BIAS MAGNETIC FIELD OF PHOTOMAGNETIC RECORDING HEAD

摘要

PURPOSE:To minimize the generation of heat of a bias magnetic field coil by superposing the focusing servo signal on the drive current for bias magnetic field coil obtained in the erasion and write modes after amplification and subtraction. CONSTITUTION:An image forming error detector 6 detects the image forming state onto a disk for the luminous flux given from a light source and outputs an image forming error as an electric signal. This signal output is amplified by a focusing servo amplifier 7 and applied to a focusing servo coil 2. The winding of the coil 2 and the phase of the output of the amplifier 7 applied to said winding are selected so that position of an image forming lens is corrected in terms of negative feedback and the luminous flux is always formed correctly on the disk. The input voltage of a terminal (2) is mixed with the voltage of a terminal (1) with the phase obtained by subtracting the voltage of the voltage of the terminal (2) from that of the terminal (1). A bias amplifier 9 amplifies the output of a mixing amplifier 8 and applies it to a bias magnetic field coil 4.