| 摘要 |
PURPOSE:To improve the precision of light output control by providing a low-pass filter holder. CONSTITUTION:At the time of reproducing, a high frequency module (M) 4 is turned on to perform the light output control. At the time of erasing and recording, a switch (S) 18 is turned off and a current source 2 keeps the just preceding current value, and the M 4 is turned off and an S 23 is opened, and a current subtractor 20 subtracts a preliminarily set pointer current. The initial current value of a current source 13 is set to a value approximately equal to a pulse current value; and with respect to the control voltage of the source 13 at the time of erasing and recording, the reference signal obtained by a low-pass filter 21 is subtracted from the monitor voltage of the light output, which is obtained by a photo diode (D) 7 and a current voltage converter 8, by a subtractor 22 and the result is subjected to low-pass filtering by a resistor 16 and a capacitor 14 to obtain this control voltage of the source 13. At the time of recording, the output obtained by subjecting the actual light output to low-pass filtering appears as the output of the converter 8 by the frequency characteristic of the D 7, the wiring capacity of the D 7 and the converter 8, and the reference signal used for the output control is subjected to low-pass filtering also; and the light output is stably controlled at the time of recording and reproducing also. Thus, the precision of light output control is improved. |
