| 摘要 |
PURPOSE:To avoid the focus error signal from receiving effects of the tracking control by setting a laser light source so that the laser luminous flux is set at about 45 to the radius direction of an optical disk and also setting a 4-split photosensor so that the orthogonal axis of this photosensor is set at about 45 deg. to the caustic curve direction. CONSTITUTION:A laser light source 1 is set so that a laser luminous flux 2 is set at about 45 deg. to the radius direction of an optical disk 5, i.e., to the direction R when the flux 2 is projected in parallel onto the disk 5. Thus the caustic curve of the focused light 6 is set at 45 deg. to the direction R of the disk 5. Therefore a 4-split photosensor 7 must be set so that the orthogonal axis of the photosensor 7 is set at about 45 deg. to the caustic curve direction of the light 6. Thus the focus error signal is obtained from the photosensor 7. In other words, the photosensor 7 is set so that one side (r) of the orthogonal axis of the photosensor 7 is coincident with the direction R of the disk 5 in case the disk 5 is set in parallel to the photosensor 7. |
