| 摘要 |
PROBLEM TO BE SOLVED: To control the output of a laser of the time when a pit is formed, by the actual time. SOLUTION: Turn back light receiving signals A, B, C, D of a main beam 16a are added by an adding amplifier 32 to obtain the value of A+B+C+D. In parallel with this calculation, turn back light receiving signals E, F of a preceding sub-beam 16b are added by an adding amplifier 34 to obtain the value of E+F. The value of (A+B+C+D)-k(E+F) is obtained by a subtraction circuit 38. By a comparator 48, the deviation between the initial value of (A+B +C+D)-k(E+F) and the value at each time point in the course of recording operation is obtained, then the output of the laser beam of the time when the pit is formed, is increased or decreased so as to negate the deviation. |
