| 摘要 |
PURPOSE:To facilitate a focus offsetting adjustment by obtaining a focus error signal with the output difference between first and second parts of a light- receiving element and obtaining an information signal with the sum of the output of first-third parts. CONSTITUTION:A light receiving element 7 is divided into five areas 7a-7f and a dividing line A0 is provided with a small angle approximately in the same direction as a diffraction direction in order to prevent the generation of a focus offsetting due to a wavelength change. Here, at the time of the focusing condition, a main beam diffracted by an area 3a of a diffraction element 3 is converged, onto the dividing line A0 of a five-divided light receiving element 7, a spot P1 is formed, and the main beam diffracted by an area 3b is converged to a light receiving part 7c and a spot P2 is formed. A focus error signal is obtained at Sa-Sb by output signals Sa-Sf of the light receiving parts 7a-7f and a pit signal is obtained at Sa+Sb+Sc by tracking error signals Se-Sf. Thus, the focus offsetting adjustment is facilitated. |
