| 摘要 |
PURPOSE:To prevent incidence of ghosts and flares to a light receiving means and to enable focus detection wit high accuracy by setting the distance measurement region on a desired imaging plane so as to deviate from the region formed as a projection pattern is moved point-symmetrically with the optical axis of an objective lens. CONSTITUTION:The ghosts are generated in the region 74. The region 72 is the range where strong ghost light enters, the region 73 is then range where the middle ghost light enters, and the region 74 is the range where the slight ghost light enters. Namely, the strong ghost is generated in the position where the slit projecting part turns back with respect to the optical axis of the objective lens. The distance measurement region on the desired imaging plane by the 2nd detecting system is, therefore, set in the region deviated from the region 72 formed as the projection pattern is moved point-symmetrically with the optical axis of the objective lens. The ghosts and flares are thereby prevented from entering the light receiving means and the focus detector which is capable of making the focus detection with always high accuracy is obtd. |
