| 摘要 |
PROBLEM TO BE SOLVED: To generate a large track cross signal even with respect to media, whose track pitches are narrow, and also to generate the track cross signal even with respect to media, in which width of land and width of groove are equal to each other by generating the track cross signal for measuring the number of tracks from the luminous flux of the center part of a reflected light from an optical disk. SOLUTION: The laser luminous flux emitted from a light source LD 101 is converged with a half mirror 104 and an objective lens 102 on the recording surface of an optical dusk 103 to be reflected on the surface. The reflected luminous flux passes through an original optical path to be divided in two directions by a beam splitter 105 and one side of the flux is received with a quadripartite PD 106 to generate a reproduced signal with quadripartite sum signals by performing a focus control and a track control. Moreover, other side of the flux passes through a light shielding member 108 and only the center part of the flux is received by a non-divided PD 107 and a track cross signal is generated by a signal generating part 110. |
