| 摘要 |
PURPOSE:To perform precise focusing detection by using two arrays of photodetecting elements and two arrays of lateral shift optical systems and shifting the lateral shift optical systems in phase by a half pitch. CONSTITUTION:A photodetecting element group is formed in two arrays 30A and 30B and stripe masks are also formed in two arrays 30A and 30B and supported on a transparent substrate 32. The 1st stripe mask array 30A and the 2nd stripe mask array 30B shift in phase by a half pitch, so when the edge of a step image is on a line A0-A0' in a figure, an evaluation function value F1 obtained from the output of the photodetecting element group 31A varies with a defocusing extent as shown by a solid line 21A in a graph. Then, an evaluation function F2 obtained from the output of the photodetecting element group 31B varies with a defocusing extent as shown by a dashed line 21B in the graph. For the purpose, the evaluation functions F1 and F2 are added together to cancel disorder near the focusing point of the evaluation functions. |
