| 摘要 |
PURPOSE:To ensure the recording with uniform quality by providing an averaging means for output of a monitor sensor and a detection means which detects the difference between the output level of the averaging means and a prescribed level and controlling the drive current of a light source in response to the output of said detection means. CONSTITUTION:The output of a monitor sensor 4 set into a position close to a laser diode 1 is averaged by an averaging means consisting of an LPF 5 and an operational amplifier 6. It is decided by a comparator 9 whether the averaged output (c) is less than the target values (Vh, Vl) or not. If the output (c) exceeds the target values, a counter 11 performs subtraction. While the counter 11 performs addition when the output (c) is less than the target values. For the counting timing, a timer 12 sends the timing signal to a counting gate 10 based on a signal (a) so that the counting action is started at a time point when the output (c) is stabilized after a writing action is started. The count value is converted into analog signals by a D/A converter 13 for control of a recording current source 3. |
