| 摘要 |
PURPOSE:To prevent a track traverse signal from being leaked to a focus error signal by adding photoelectric conversion outputs from light receiving faces which are not adjacent out of four peripheral light receiving faces orthogonal to one another to generate two outputs and using the difference between these two outputs as the focus error signal. CONSTITUTION:A photoelectric transducer 8' consists of a central light receiving face 9 whose shape and dimensions are approximately equal to those of a minimum circle of confusion generated by an astigmatism generating optical system and peripheral light receiving faces 10 to 13 arranged around the light receiving face 9 along the direction of astigmatism generation. In this case, the spot on light receiving faces 10 to 13 of the photoelectric transducer 8' is deformed to a rightward rising and approximately elliptic form, an approximately circular form, and a leftward rising and approximately elliptic form in accordance with the distance between an optical disk and an objective lens. When the difference between the total photoelectric conversion output of peripheral light receiving faces 10 and 12 and that of peripheral light receiving faces 11 and 13 is obtained as focus error signal, the leakage of the track row traverse signal to the focus error signal is very reduced. Thus, accurate tracking is possible. |
