光电探测器(PDIC)的安装误差导致光学头的光学轴心与光电探测器的中心不重合。在光盘标量衍射模型的基础上，引入光电探测器的位置误差参数，根据DVD－ROM的盘片参数，计算并分析了位置误差对差动相位探测(DPD)信号的影响。计算结果表明：沿盘片切向的位置误差使DPD的幅值变小，在25%的范围内DPD的幅值随切向位置误差的变化系数为1．52T；沿盘片径向的位置误差使DPD产生直流偏置，在50%的范围内DPD直流偏置随径向位置误差的变化系数为3．8T。

The PDIC (Photo detector integrated circuit) position error causes the displacement between the optic axis of optical pick-up and the PDIC center. The influence of PDIC position error on the DPD (Differential phase detection) signal is analyzed and computed using the DVD-ROM parameters based on the optic disk scalar diffraction model. The poison error along disk tangential direction decreases the DPD signal amplitude,and the factor is 1.52T when position error is less than 25%.The radial poison error increases the DPD signal offset,and the factor is 3.8T when position error is less than 50%.