| 摘要 |
PURPOSE:To focus a camera on a low-contrast distant object surely by inclining the base line of an optical system, which projects the object image, with respect to a focusing screen and arranging it in accordance with a focus detection module. CONSTITUTION:Fixed and scanning mirrors 1 and 2 are so arranged that the base line connecting their centers is inclined at an angle theta to the horizontal straight angle of the screen in case of horizontal arrangement of the camera or to a horizontal side of the field angle. Since a mountain and the sky are covered in the part of a visual field Fi due to the mirror 1, outputs of photodetector groups corresponding to mirrors 1 and 2 in case of the closest optical distance scanning are different from each other. Outputs of these photodetector groups approach coincidence gradually according as scanning is shifted from the closest distance to the infinity, and correlations are obtained when scanning reaches the infinity. Thus, the camera is focused surely on the low-contrast distant object. |
