| 摘要 |
PURPOSE:To simplify a detecting circuit by arranging two detectors of a four- division photodetectors so that one-side parts face each other and arranging the remaining detectors on both sides of them, and connecting them in parallel so that the output voltages of the opposite detectors are reverse. CONSTITUTION:The four-division photodetector 15 is so constituted that the detectors A and B among four divided detectors arranged each having one side opposite and the remaining detectors C and D are arranged above and below them respectively. Then the opposite detectors A and B, and C and D are connected in parallel so that their output voltages are opposite; and one is grounded and the other is connected to amplifiers 21 and 22. Consequently, the up/down movement of a light beam 20 is obtained by the detectors C and D and the right/left movement is obtained by the detectors A and B. Namely, a focus signal Ef at the time of a two-dimensional actuator is obtained as Ef=C-D and a tracking signal Et is obtained as Et=A-B. Thus, the number of signal lines is decreased and following circuits are simplified.
|
