| 摘要 |
PURPOSE:To obtain an exact tracking control signal or focusing control signal by executing arrangement in a distance to be equal from a light source so that a direct light from the light source can be equally incoming to an optical detector which goes to be functionally a pair with plural optical detecting parts to constitute the optical detector. CONSTITUTION:Optical detecting parts 10e and 10f, which have equal areas respectively and go to be the pair functionally, for tracking error detection, for example, are arranged so as to be the equal distance to a laser diode 1. Thus, even when an unnecessary light, out of an outgoing light flux from the laser diode 1, is dispersed in an optical detector edge 24 of the optical detector 10 and incoming to optical detecting parts 10a-10d of the optical detector 10, since the unnecessary light to be incoming to the optical detecting parts 10e and 10f, which go to be the pair functionally, is almost equal, the unnecessary light is canceled in the differential output of the both optical detecting parts 10e and 10f and the influence of the light is ignored. Thus, the exact tracking error signal can be obtained. |
