| 摘要 |
PURPOSE:To accurately detect a focus error by providing a luminous flux dividing means which divides the reflected light into four specific areas, a focusing means, a polarized light separating means, and a photodetecting means. CONSTITUTION:A 4-split prism 8 divides the reflected light at least into the interference light of the +1-order diffracted light and the 0-order diffracted light, the interference light of the -1-order diffracted light and the 0-order diffracted light and the 1st and 2nd light areas. A focusing lens 6 focuses those four divided luminous fluxes to each specified position. A polarized light separating means 5 separates the divided luminous fluxes into two polarized components orthogonal to each other. Then a 12-split photodetector 9 detects at least eight luminous fluxes obtained finally by the means 5 independently of each other. |
