| 摘要 |
PURPOSE:To improve the assembling efficiency of an optical pickup by adjusting an offset voltage so that a focus signal is zero at focusing state thereby generating easily and surely a proper focus signal. CONSTITUTION:A difference between an output (X1-X2)/(X1+X2) and an offset voltage Y is outputted from an amplifier 38. An output Z1 is a focus signal and an output Z10 when the offset voltage Y is adjusted to obtain Z1=0 at focus state is expressed in equation and used as the focus signal, and the variance part (the 1st term of the right side of the equation) in the focus signal Z10 is expressed as a ratio of the sum to the difference in the outputs X1, X2, even when the luminous amount of the incident luminous flux is changed, the effect is not imposed on the focusing. Thus, a proper focus signal is generated to a spot of a converging luminous flux without adjusting the position of the semiconductor detector with high accuracy. Thus, the assembly efficiency of the optical pickup is improved. |
