| 摘要 |
<P>PROBLEM TO BE SOLVED: To control the power of a laser beam in a simple and inexpensive circuit configuration without being limited by a current/voltage converter's passband. <P>SOLUTION: A photo diode 141 monitors the laser beam emitted from a semiconductor laser 131. The output current I<SB>PD</SB>of the photo diode 141 is charged by a capacitor 143 making up the charging circuit. The connecting switch 144 forms a discharging circuit. The APC circuit 116 controls the current sources 136-138 which constitute the laser driver 132 based on the charging voltage during the predetermined period (for example, a period to form a record mark, or a DC period not forming the record mark), and stabilizes the laser power (peak power, bottom power in the modulating period, and erasing power in the DC period). Since a current/voltage converter is not used to convert the output current I<SB>PD</SB>into voltage signals, the circuit configuration becomes simple and inexpensive and thus not influenced by the converter which has a limit in its passband. <P>COPYRIGHT: (C)2006,JPO&NCIPI |
