2-2. Focus Servo
The aim of Focus Servo is to maintain the distance between object lens of P/U and disc surface, so that the
detected RF signal(A, B, C, D, EF1, EF2, EF3, EF4) can be maximized.
Focus Error Signal(FE) generates from focus error detection block in RF IC(R2S35002) using Conventional
Astigmatism Detection method, Differential Astigmatism Detection method.
Focus Gain and path can be changed at the RF IC(R2S35002) according to the disc, and the resulting output
FE(R2S35002 2pin) is input to DSP IC(R2S35002 169pin).
The Focus Search operation is using FE, PE Signal, therefore check FE, PE signals when Focusing is failed.
The role of DSP IC(R8J32007) is Focus Digital Controller. The operation path is as follows;
FE Signal is input to DSP IC(R8J32007 169pin), and after A/D Conversion, Digital Equalizer Block and D/A
Conversion in R8J32006FP, the output signal FOD(R8J32007 180pin) is input to Drive IC(R2S30202FP 40pin).
The drive output signal FACT+/FACT- generated according FOIN(R2S30202FP 40pin), and drives focus
actuator in the P/U unit.
