Error signal generating device for use in an apparatus for optically reading information with a resistance network connected to photo detector elements

摘要

A servo device for use with a system for reading out recorded information having at least two pickup elements which produce pickup signals comprising a resistance network including at least a resistance through which at least two of the pickup signals flow, and an error signal producing device for producing a tracking error signal and a focusing error signal in accordance with a voltage level developed at a terminal of the resistance, whereby eliminating the use of a plurality of amplifying circuits and adder circuits which are respectively connected to each of pickup elements, and enabling the production of more accurate error signals and reduction of the cost of the servo device.