| 摘要 |
PURPOSE:To jump between different tracks on an optical disc instantaneously by forming two pairs of photodetecting parts for detecting light reflected from respective tracks on a photoelectric conversion element. CONSTITUTION:A diffraction grating 20 having a least two optical grating surfaces 21a, 22a of which grating directions intersect almost at right angles each other and irragiating three beams to each of at least two tracks of the optical disc 7 is arranged between a semiconductor laser 1 to be a light source and a separated optical system in a focusing optical system consisting of a collimater lens 2, a 1/4 wavelength plate 5, an objective lens 6, and the diffraction grating 20. On the other hand, at least two pairs of photodetecting parts for detecting respective reflected lights from respective tracks are formed on the photoelectric conversion element 26. |
