| 摘要 |
PURPOSE:To attain tracking control with high accuracy by using a detecting means for deviation amount (deflection amount) of a tangential mirror (mobile mirror) of a tangential servo device and correcting a tracking error signal in response to the output of said detecting means. CONSTITUTION:A difference [(a+b)-(c+d)] between the addition outputs of adders 15 and 16 is obtained by a subtractor 18. The difference output of the subtractor 18 is used as the comparison inputs of comparators 19 and 20 having reference levels +VTH and -VTH respectively. The comparison output of the comparator 19 is used as a control signal which turns on (closes) a switch S2. Thus a tangential mirror is deflected in response to a tangential error signal. When the amplitude of the tangential mirror exceeds a reference level, a control signal is produced from the comparator 19 or 20 according to the deflecting direction of the tangential mirror. Then a switch S2 or S1 is turned on in response to said control signal. Thus a tracking error signal is corrected in the positive or negative direction. |
