| 摘要 |
PURPOSE:To ensure a stable automatic tracking servo action by using the output of an adder which adds all outputs of an amplifier that amplifies the output of a subtractor with an optional amplification factor as a tracking error signal. CONSTITUTION:A light detector consists of the photodetectors 7c-7f set in parallel to an information track with the same level of photodetecting sensitivity. The difference (E-D) between the detection outputs E and D of both photodetectors 7e and 7d is obtained by a subtractor 501. At the same time, the difference (F-C) between the detection outputs F and C of both photodetector 7f and 7c is obtained by a subtractor 502. This difference (F-C) is amplified double by an amplifier 503. Then an adder 504 adds the values (E-D) and 2(F-C) together and this added value (E-D)+2(F-C) is used as a tracking error signal. Thus a stable automatic tracking servo action is realized against the external impacts, etc. |
