| 摘要 |
PURPOSE:To derive the best information read signal and a tracking error signal from an information read beam according to the depth of pits, by arranging a couple of photoelectric converting elements in such a way that they coincide with the optical axis of the objective lens for a disk. CONSTITUTION:A read beam from a laser 5 is modulated according to the depth of a pit 10 of a disk 1, and a total reflection beam from a reflecting film is caused to illuminate a photoelectric converting element couple 12. The element couple 12 are arranged on the surface where diffracted beams differing in degree among reflected beams are discriminated sufficiently, the origin O is set on the optical axis of an objective lens 7, and the X axis and Y axis of an orthogonal coordinate system coincide with the tangent and normal directions of a track 4. Outputs of the elements in the opposite quadrants are added at parts 13 and 14, and the sums are further processed by subtraction 15 and addition 16; the sum signal is led out as an RF signal and shifted in phase by 90 deg. at a part 17, and the resulting signal is multiplied by the subtraction output DF at a part 18, thereby outputting a tracking error signal eT through an LRF19. |
