| 摘要 |
<P>PROBLEM TO BE SOLVED: To solve the problem of a visual field property that a differential push/pull signal amplitude is deteriorated markedly with displacement of an objective lens etc. in a detection system, which is disclosed conventionally, using an in line type DPP (differential push/pull) system as a system for detecting a tracking error signal with respect to a plurality of kinds of optical disks whose track pitches are different from one another. <P>SOLUTION: As a branching means, this optical pickup is provided with a diffraction grating divided into at least three areas of first, second and third areas and provided with a prescribed periodical structure in each area. The first area is arranged between the second and third areas. In the second area, a periodical structure having a phase different by nearly 90° from the phase of a periodical structure provided in the first area is provided. In the third area, a periodical structure having a phase different by nearly 180° from the phase of a periodical structure provided in the second area is provided. <P>COPYRIGHT: (C)2006,JPO&NCIPI |
