聚焦误差信号的产生采用象散射法。当激光束的焦点落在光盘轨迹上时,PD的A、B、C、D四个象限产生等量的输出信号,如图2(b),经过减法器,其聚焦误差信号FE=(A+C)-(B+D)=0。若焦点不在正确位置上,或近或远,则FE≠0.FE信号从N101①输出,经R142、R141输入N101②,经内部聚焦相 The focus error signal is generated using the astigmatic method. When the focal point of the laser beam falls on the track of the optical disc, the four quadrants A, B, C and D of the PD produce the same amount of output signals, as shown in Fig. 2 (b), after the subtractor, the focus error signal FE = + C) - (B + D) = 0. If the focus is not in the correct position, near or far, then FE ≠ 0.FE signal output from N101 ①, R142, R141 input N101 ②, by the internal focus phase