| 摘要 |
PURPOSE:To improve the accuracy of detection by detecting the error of tracking and focusing by comparing the quantity of returned light diffracted by the more than two divided areas for tracking and focusing of a diffracting element and received by light receiving areas for tracking and focusing in a light receiving element. CONSTITUTION:The tracking error is detected by comparing the quantity of the returning light diffracted by more than two divided areas 12a and 12c of a diffracting element 12 and received by light receiving area 17c and 17d for tracking. The focusing error is detected by comparing the quantity of the returned light diffracted by the divided area 12a for focusing in the diffracting element 12 and received by two adjacent light receiving areas 17a and 17b for focusing in a photodetector 17. On the other hand, even when a beam for focusing error detection is finely adjusted on the photodetector spread by the dispersion of performance, the beam for focusing error detection is not affected by the light intensity distribution to be changed according to a light beam irradiating position to the track. |
