Diffraction element and optical pick-up apparatus having the same

摘要

A diffraction element (160) for an optical pick-up apparatus is capable of precisely controlling the tracking of the pick-up apparatus. The diffraction element (160) includes a diffraction grating divided into a first, a second, and a third region (166). The second region (164) is located between the first and third regions (162,166). Any one of the first region (162) and the third region (166) is inclined at a predetermined angle ¸ with respect to the second region (164).